diff --git a/CHANGES b/CHANGES
index 7ab5186a6..2eb8905ff 100644
--- a/CHANGES
+++ b/CHANGES
@@ -6,6 +6,7 @@ Here you can find the recent changes to libtmux
 
 current
 -------
+- :issue:`234`: ``Window.split_window``: Allow passing ``percent``
 - :issue:`289`: Fix warning due to invalid escape sequences
 - :issue:`295`: Publish docs via our own action
 - :issue:`295`: Move more packaging over to poetry, though we'll keep
diff --git a/libtmux/pane.py b/libtmux/pane.py
index 5ea1f11f9..0be1d8151 100644
--- a/libtmux/pane.py
+++ b/libtmux/pane.py
@@ -155,7 +155,7 @@ def reset(self):
 
         self.cmd('send-keys', r'-R \; clear-history')
 
-    def split_window(self, attach=False, vertical=True, start_directory=None):
+    def split_window(self, attach=False, vertical=True, start_directory=None, percent=None):
         """
         Split window at pane and return newly created :class:`Pane`.
 
@@ -167,6 +167,8 @@ def split_window(self, attach=False, vertical=True, start_directory=None):
             split vertically
         start_directory : str, optional
             specifies the working directory in which the new pane is created.
+        percent: int, optional
+            percentage to occupy with respect to current pane
 
         Returns
         -------
@@ -177,6 +179,7 @@ def split_window(self, attach=False, vertical=True, start_directory=None):
             start_directory=start_directory,
             attach=attach,
             vertical=vertical,
+            percent=percent,
         )
 
     def set_width(self, width):
diff --git a/libtmux/window.py b/libtmux/window.py
index 7b5b1b1d6..05ee34c33 100644
--- a/libtmux/window.py
+++ b/libtmux/window.py
@@ -382,7 +382,13 @@ def last_pane(self):
         return self.select_pane('-l')
 
     def split_window(
-        self, target=None, start_directory=None, attach=True, vertical=True, shell=None
+        self,
+        target=None,
+        start_directory=None,
+        attach=True,
+        vertical=True,
+        shell=None,
+        percent=None,
     ):
         """
         Split window and return the created :class:`Pane`.
@@ -407,6 +413,8 @@ def split_window(
             NOTE: When this command exits the pane will close.  This feature
             is useful for long-running processes where the closing of the
             window upon completion is desired.
+        percent: int, optional
+            percentage to occupy with respect to current window
 
         Returns
         -------
@@ -446,6 +454,9 @@ def split_window(
         else:
             tmux_args += ('-h',)
 
+        if percent is not None:
+            tmux_args += ('-p %d' % percent,)
+
         tmux_args += ('-P', '-F%s' % ''.join(tmux_formats))  # output
 
         if start_directory: