diff --git a/sklearn/model_selection/_split.py b/sklearn/model_selection/_split.py
index fbc00f3069e51..113a015c2bbca 100644
--- a/sklearn/model_selection/_split.py
+++ b/sklearn/model_selection/_split.py
@@ -1706,12 +1706,19 @@ def _validate_shuffle_split(n_samples, test_size, train_size):
 class PredefinedSplit(BaseCrossValidator):
     """Predefined split cross-validator
 
-    Splits the data into training/test set folds according to a predefined
-    scheme. Each sample can be assigned to at most one test set fold, as
-    specified by the user through the ``test_fold`` parameter.
+    Provides train/test indices to split data into train/test sets using a
+    predefined scheme specified by the user with the ``test_fold`` parameter.
 
     Read more in the :ref:`User Guide <cross_validation>`.
 
+    Parameters
+    ----------
+    test_fold : array-like, shape (n_samples,)
+        The entry ``test_fold[i]`` represents the index of the test set that
+        sample ``i`` belongs to. It is possible to exclude sample ``i`` from
+        any test set (i.e. include sample ``i`` in every training set) by
+        setting ``test_fold[i]`` equal to -1.
+
     Examples
     --------
     >>> from sklearn.model_selection import PredefinedSplit