diff --git a/lldb/source/Commands/CommandObjectWatchpoint.cpp b/lldb/source/Commands/CommandObjectWatchpoint.cpp
--- a/lldb/source/Commands/CommandObjectWatchpoint.cpp
+++ b/lldb/source/Commands/CommandObjectWatchpoint.cpp
@@ -823,6 +823,16 @@
 
   ~CommandObjectWatchpointSetVariable() override = default;
 
+  void
+  HandleArgumentCompletion(CompletionRequest &request,
+                           OptionElementVector &opt_element_vector) override {
+    if (request.GetCursorIndex() != 0)
+      return;
+    CommandCompletions::InvokeCommonCompletionCallbacks(
+        GetCommandInterpreter(), CommandCompletions::eVariablePathCompletion,
+        request, nullptr);
+  }
+
   Options *GetOptions() override { return &m_option_group; }
 
 protected:
diff --git a/lldb/test/API/functionalities/completion/TestCompletion.py b/lldb/test/API/functionalities/completion/TestCompletion.py
--- a/lldb/test/API/functionalities/completion/TestCompletion.py
+++ b/lldb/test/API/functionalities/completion/TestCompletion.py
@@ -209,6 +209,13 @@
         """Test that 'watchpoint set var' completes to 'watchpoint set variable '."""
         self.complete_from_to('watchpoint set var', 'watchpoint set variable ')
 
+    def test_watchpoint_set_variable_foo(self):
+        self.build()
+        lldbutil.run_to_source_breakpoint(self, '// Break here', lldb.SBFileSpec("main.cpp"))
+        self.complete_from_to('watchpoint set variable fo', 'watchpoint set variable fooo')
+        # Only complete the first argument.
+        self.complete_from_to('watchpoint set variable fooo ', 'watchpoint set variable fooo ')
+
     def test_help_fi(self):
         """Test that 'help fi' completes to ['file', 'finish']."""
         self.complete_from_to(