diff --git a/src/mlpack/methods/decision_tree/decision_tree.hpp b/src/mlpack/methods/decision_tree/decision_tree.hpp
index e8cc7d08ca..eec026c92f 100644
--- a/src/mlpack/methods/decision_tree/decision_tree.hpp
+++ b/src/mlpack/methods/decision_tree/decision_tree.hpp
@@ -15,20 +15,9 @@
 
 #include <mlpack/core.hpp>
 
-#include "gini_gain.hpp"
-#include "information_gain.hpp"
-#include "mad_gain.hpp"
-#include "mse_gain.hpp"
-
-#include "best_binary_numeric_split.hpp"
-#include "random_binary_numeric_split.hpp"
-
-#include "best_binary_categorical_split.hpp"
-#include "all_categorical_split.hpp"
-
-#include "all_dimension_select.hpp"
-#include "random_dimension_select.hpp"
-#include "multiple_random_dimension_select.hpp"
+#include "fitness_functions/fitness_functions.hpp"
+#include "split_functions/split_functions.hpp"
+#include "select_functions/select_functions.hpp"
 
 namespace mlpack {
 
diff --git a/src/mlpack/methods/decision_tree/decision_tree_regressor.hpp b/src/mlpack/methods/decision_tree/decision_tree_regressor.hpp
index 67f50695a8..67c9b9ad9c 100644
--- a/src/mlpack/methods/decision_tree/decision_tree_regressor.hpp
+++ b/src/mlpack/methods/decision_tree/decision_tree_regressor.hpp
@@ -15,12 +15,9 @@
 
 #include <mlpack/core.hpp>
 
-#include "mad_gain.hpp"
-#include "mse_gain.hpp"
-#include "best_binary_numeric_split.hpp"
-#include "all_categorical_split.hpp"
-#include "random_binary_numeric_split.hpp"
-#include "all_dimension_select.hpp"
+#include "fitness_functions/fitness_functions.hpp"
+#include "split_functions/split_functions.hpp"
+#include "select_functions/select_functions.hpp"
 
 namespace mlpack {
 
diff --git a/src/mlpack/methods/decision_tree/fitness_functions/fitness_functions.hpp b/src/mlpack/methods/decision_tree/fitness_functions/fitness_functions.hpp
new file mode 100644
index 0000000000..2ee82c29ca
--- /dev/null
+++ b/src/mlpack/methods/decision_tree/fitness_functions/fitness_functions.hpp
@@ -0,0 +1,4 @@
+#include "gini_gain.hpp"
+#include "information_gain.hpp"
+#include "mad_gain.hpp"
+#include "mse_gain.hpp"
\ No newline at end of file
diff --git a/src/mlpack/methods/decision_tree/gini_gain.hpp b/src/mlpack/methods/decision_tree/fitness_functions/gini_gain.hpp
similarity index 99%
rename from src/mlpack/methods/decision_tree/gini_gain.hpp
rename to src/mlpack/methods/decision_tree/fitness_functions/gini_gain.hpp
index ea7d4a5407..34f6c4a7fb 100644
--- a/src/mlpack/methods/decision_tree/gini_gain.hpp
+++ b/src/mlpack/methods/decision_tree/fitness_functions/gini_gain.hpp
@@ -1,5 +1,5 @@
 /**
- * @file methods/decision_tree/gini_gain.hpp
+ * @file methods/decision_tree/fitness_functions/gini_gain.hpp
  * @author Ryan Curtin
  *
  * The GiniGain class, which is a fitness function (FitnessFunction) for
diff --git a/src/mlpack/methods/decision_tree/information_gain.hpp b/src/mlpack/methods/decision_tree/fitness_functions/information_gain.hpp
similarity index 98%
rename from src/mlpack/methods/decision_tree/information_gain.hpp
rename to src/mlpack/methods/decision_tree/fitness_functions/information_gain.hpp
index 7cf0f1158e..9c6719a23a 100644
--- a/src/mlpack/methods/decision_tree/information_gain.hpp
+++ b/src/mlpack/methods/decision_tree/fitness_functions/information_gain.hpp
@@ -1,5 +1,5 @@
 /**
- * @file methods/decision_tree/information_gain.hpp
+ * @file methods/decision_tree/fitness_functions/information_gain.hpp
  * @author Ryan Curtin
  *
  * An implementation of information gain, which can be used in place of Gini
diff --git a/src/mlpack/methods/decision_tree/mad_gain.hpp b/src/mlpack/methods/decision_tree/fitness_functions/mad_gain.hpp
similarity index 97%
rename from src/mlpack/methods/decision_tree/mad_gain.hpp
rename to src/mlpack/methods/decision_tree/fitness_functions/mad_gain.hpp
index 742700fb34..908af9b966 100644
--- a/src/mlpack/methods/decision_tree/mad_gain.hpp
+++ b/src/mlpack/methods/decision_tree/fitness_functions/mad_gain.hpp
@@ -1,5 +1,5 @@
 /**
- * @file methods/decision_tree/mad_gain.hpp
+ * @file methods/decision_tree/fitness_functions/mad_gain.hpp
  * @author Rishabh Garg
  *
  * The mean absolute deviation gain class, a fitness function for regression
@@ -15,7 +15,7 @@ n.
 #define MLPACK_METHODS_DECISION_TREE_MAD_GAIN_HPP
 
 #include <mlpack/prereqs.hpp>
-#include "utils.hpp"
+#include "mlpack/methods/decision_tree/utils.hpp"
 
 namespace mlpack {
 
diff --git a/src/mlpack/methods/decision_tree/mse_gain.hpp b/src/mlpack/methods/decision_tree/fitness_functions/mse_gain.hpp
similarity index 98%
rename from src/mlpack/methods/decision_tree/mse_gain.hpp
rename to src/mlpack/methods/decision_tree/fitness_functions/mse_gain.hpp
index 8e64a97a01..77687d2cd1 100644
--- a/src/mlpack/methods/decision_tree/mse_gain.hpp
+++ b/src/mlpack/methods/decision_tree/fitness_functions/mse_gain.hpp
@@ -1,5 +1,5 @@
 /**
- * @file methods/decision_tree/mse_gain.hpp
+ * @file methods/decision_tree/fitness_functions/mse_gain.hpp
  * @author Rishabh Garg
  *
  * The mean squared error gain class, which is a fitness funtion for
@@ -14,7 +14,7 @@
 #define MLPACK_METHODS_DECISION_TREE_MSE_GAIN_HPP
 
 #include <mlpack/prereqs.hpp>
-#include "utils.hpp"
+#include <mlpack/methods/decision_tree/utils.hpp>
 
 namespace mlpack {
 
diff --git a/src/mlpack/methods/decision_tree/all_dimension_select.hpp b/src/mlpack/methods/decision_tree/select_functions/all_dimension_select.hpp
similarity index 95%
rename from src/mlpack/methods/decision_tree/all_dimension_select.hpp
rename to src/mlpack/methods/decision_tree/select_functions/all_dimension_select.hpp
index 332a439fd8..5c59a6f60c 100644
--- a/src/mlpack/methods/decision_tree/all_dimension_select.hpp
+++ b/src/mlpack/methods/decision_tree/select_functions/all_dimension_select.hpp
@@ -1,5 +1,5 @@
 /**
- * @file methods/decision_tree/all_dimension_select.hpp
+ * @file methods/decision_tree/select_functions/all_dimension_select.hpp
  * @author Ryan Curtin
  *
  * Selects all dimensions for a split.
diff --git a/src/mlpack/methods/decision_tree/multiple_random_dimension_select.hpp b/src/mlpack/methods/decision_tree/select_functions/multiple_random_dimension_select.hpp
similarity index 96%
rename from src/mlpack/methods/decision_tree/multiple_random_dimension_select.hpp
rename to src/mlpack/methods/decision_tree/select_functions/multiple_random_dimension_select.hpp
index 6ce277d258..d0c3fff36a 100644
--- a/src/mlpack/methods/decision_tree/multiple_random_dimension_select.hpp
+++ b/src/mlpack/methods/decision_tree/select_functions/multiple_random_dimension_select.hpp
@@ -1,5 +1,5 @@
 /**
- * @file methods/decision_tree/multiple_random_dimension_select.hpp
+ * @file methods/decision_tree/select_functions/multiple_random_dimension_select.hpp
  * @author Ryan Curtin
  *
  * Select a number of random dimensions to pick from.
diff --git a/src/mlpack/methods/decision_tree/random_dimension_select.hpp b/src/mlpack/methods/decision_tree/select_functions/random_dimension_select.hpp
similarity index 95%
rename from src/mlpack/methods/decision_tree/random_dimension_select.hpp
rename to src/mlpack/methods/decision_tree/select_functions/random_dimension_select.hpp
index fdf024a70a..03a32f5fc2 100644
--- a/src/mlpack/methods/decision_tree/random_dimension_select.hpp
+++ b/src/mlpack/methods/decision_tree/select_functions/random_dimension_select.hpp
@@ -1,5 +1,5 @@
 /**
- * @file methods/decision_tree/random_dimension_select.hpp
+ * @file methods/decision_tree/select_functions/random_dimension_select.hpp
  * @author Ryan Curtin
  *
  * Selects one single random dimension to split on.
diff --git a/src/mlpack/methods/decision_tree/select_functions/select_functions.hpp b/src/mlpack/methods/decision_tree/select_functions/select_functions.hpp
new file mode 100644
index 0000000000..da857189f1
--- /dev/null
+++ b/src/mlpack/methods/decision_tree/select_functions/select_functions.hpp
@@ -0,0 +1,3 @@
+#include "all_dimension_select.hpp"
+#include "multiple_random_dimension_select.hpp"
+#include "random_dimension_select.hpp"
\ No newline at end of file
diff --git a/src/mlpack/methods/decision_tree/all_categorical_split.hpp b/src/mlpack/methods/decision_tree/split_functions/all_categorical_split.hpp
similarity index 98%
rename from src/mlpack/methods/decision_tree/all_categorical_split.hpp
rename to src/mlpack/methods/decision_tree/split_functions/all_categorical_split.hpp
index 3165e6791e..d9e07e6a20 100644
--- a/src/mlpack/methods/decision_tree/all_categorical_split.hpp
+++ b/src/mlpack/methods/decision_tree/split_functions/all_categorical_split.hpp
@@ -1,5 +1,5 @@
 /**
- * @file methods/decision_tree/all_categorical_split.hpp
+ * @file methods/decision_tree/split_functions/all_categorical_split.hpp
  * @author Ryan Curtin
  *
  * This file defines a tree splitter that split a categorical feature into all
diff --git a/src/mlpack/methods/decision_tree/all_categorical_split_impl.hpp b/src/mlpack/methods/decision_tree/split_functions/all_categorical_split_impl.hpp
similarity index 98%
rename from src/mlpack/methods/decision_tree/all_categorical_split_impl.hpp
rename to src/mlpack/methods/decision_tree/split_functions/all_categorical_split_impl.hpp
index 6f0b67ef20..2e44680036 100644
--- a/src/mlpack/methods/decision_tree/all_categorical_split_impl.hpp
+++ b/src/mlpack/methods/decision_tree/split_functions/all_categorical_split_impl.hpp
@@ -1,5 +1,5 @@
 /**
- * @file methods/decision_tree/all_categorical_split_impl.hpp
+ * @file methods/decision_tree/split_functions/all_categorical_split_impl.hpp
  * @author Ryan Curtin
  *
  * Implementation of the AllCategoricalSplit categorical split class.
diff --git a/src/mlpack/methods/decision_tree/best_binary_categorical_split.hpp b/src/mlpack/methods/decision_tree/split_functions/best_binary_categorical_split.hpp
similarity index 100%
rename from src/mlpack/methods/decision_tree/best_binary_categorical_split.hpp
rename to src/mlpack/methods/decision_tree/split_functions/best_binary_categorical_split.hpp
diff --git a/src/mlpack/methods/decision_tree/best_binary_categorical_split_impl.hpp b/src/mlpack/methods/decision_tree/split_functions/best_binary_categorical_split_impl.hpp
similarity index 99%
rename from src/mlpack/methods/decision_tree/best_binary_categorical_split_impl.hpp
rename to src/mlpack/methods/decision_tree/split_functions/best_binary_categorical_split_impl.hpp
index c5be2c4de2..bd0c8f62c3 100644
--- a/src/mlpack/methods/decision_tree/best_binary_categorical_split_impl.hpp
+++ b/src/mlpack/methods/decision_tree/split_functions/best_binary_categorical_split_impl.hpp
@@ -1,5 +1,5 @@
 /**
- * @file methods/decision_tree/all_categorical_split_impl.hpp
+ * @file methods/decision_tree/split_functions/all_categorical_split_impl.hpp
  * @author Nikolay Apanasov (nikolay@apanasov.org)
  *
  * Implementation of the BestBinaryCategoricalSplit categorical split class.
diff --git a/src/mlpack/methods/decision_tree/best_binary_numeric_split.hpp b/src/mlpack/methods/decision_tree/split_functions/best_binary_numeric_split.hpp
similarity index 98%
rename from src/mlpack/methods/decision_tree/best_binary_numeric_split.hpp
rename to src/mlpack/methods/decision_tree/split_functions/best_binary_numeric_split.hpp
index bcaa27139e..79c18ee63f 100644
--- a/src/mlpack/methods/decision_tree/best_binary_numeric_split.hpp
+++ b/src/mlpack/methods/decision_tree/split_functions/best_binary_numeric_split.hpp
@@ -1,5 +1,5 @@
 /**
- * @file methods/decision_tree/best_binary_numeric_split.hpp
+ * @file methods/decision_tree/split_functions/best_binary_numeric_split.hpp
  * @author Ryan Curtin
  *
  * A tree splitter that finds the best binary numeric split.
@@ -13,7 +13,7 @@
 #define MLPACK_METHODS_DECISION_TREE_BEST_BINARY_NUMERIC_SPLIT_HPP
 
 #include <mlpack/prereqs.hpp>
-#include "mse_gain.hpp"
+#include <mlpack/methods/decision_tree/fitness_functions/mse_gain.hpp>
 
 #include <mlpack/core/util/sfinae_utility.hpp>
 
diff --git a/src/mlpack/methods/decision_tree/best_binary_numeric_split_impl.hpp b/src/mlpack/methods/decision_tree/split_functions/best_binary_numeric_split_impl.hpp
similarity index 99%
rename from src/mlpack/methods/decision_tree/best_binary_numeric_split_impl.hpp
rename to src/mlpack/methods/decision_tree/split_functions/best_binary_numeric_split_impl.hpp
index b45ab2fabf..c98af633b6 100644
--- a/src/mlpack/methods/decision_tree/best_binary_numeric_split_impl.hpp
+++ b/src/mlpack/methods/decision_tree/split_functions/best_binary_numeric_split_impl.hpp
@@ -1,5 +1,5 @@
 /**
- * @file methods/decision_tree/best_binary_numeric_split_impl.hpp
+ * @file methods/decision_tree/split_functions/best_binary_numeric_split_impl.hpp
  * @author Ryan Curtin
  *
  * Implementation of strategy that finds the best binary numeric split.
diff --git a/src/mlpack/methods/decision_tree/random_binary_numeric_split.hpp b/src/mlpack/methods/decision_tree/split_functions/random_binary_numeric_split.hpp
similarity index 98%
rename from src/mlpack/methods/decision_tree/random_binary_numeric_split.hpp
rename to src/mlpack/methods/decision_tree/split_functions/random_binary_numeric_split.hpp
index ef01a8424b..0726862a7e 100644
--- a/src/mlpack/methods/decision_tree/random_binary_numeric_split.hpp
+++ b/src/mlpack/methods/decision_tree/split_functions/random_binary_numeric_split.hpp
@@ -1,5 +1,5 @@
 /**
- * @file methods/decision_tree/random_binary_numeric_split.hpp
+ * @file methods/decision_tree/split_functions/random_binary_numeric_split.hpp
  * @author Rishabh Garg
  *
  * A tree splitter that finds a random binary numeric split.
diff --git a/src/mlpack/methods/decision_tree/random_binary_numeric_split_impl.hpp b/src/mlpack/methods/decision_tree/split_functions/random_binary_numeric_split_impl.hpp
similarity index 98%
rename from src/mlpack/methods/decision_tree/random_binary_numeric_split_impl.hpp
rename to src/mlpack/methods/decision_tree/split_functions/random_binary_numeric_split_impl.hpp
index 10d92af69c..d89daa9706 100644
--- a/src/mlpack/methods/decision_tree/random_binary_numeric_split_impl.hpp
+++ b/src/mlpack/methods/decision_tree/split_functions/random_binary_numeric_split_impl.hpp
@@ -1,5 +1,5 @@
 /**
- * @file methods/decision_tree/random_binary_numeric_split_impl.hpp
+ * @file methods/decision_tree/split_functions/random_binary_numeric_split_impl.hpp
  * @author Rishabh Garg
  *
  * Implementation of strategy that finds the random binary numeric split.
diff --git a/src/mlpack/methods/decision_tree/split_functions/split_functions.hpp b/src/mlpack/methods/decision_tree/split_functions/split_functions.hpp
new file mode 100644
index 0000000000..63d1d5cb5a
--- /dev/null
+++ b/src/mlpack/methods/decision_tree/split_functions/split_functions.hpp
@@ -0,0 +1,4 @@
+#include "all_categorical_split.hpp"
+#include "best_binary_numeric_split.hpp"
+#include "random_binary_numeric_split.hpp"
+#include "best_binary_categorical_split.hpp"
\ No newline at end of file