diff --git a/src/textual/_xterm_parser.py b/src/textual/_xterm_parser.py
index 4cc21fecc5..a81e35983b 100644
--- a/src/textual/_xterm_parser.py
+++ b/src/textual/_xterm_parser.py
@@ -18,7 +18,7 @@
 # to be unsuccessful?
 _MAX_SEQUENCE_SEARCH_THRESHOLD = 32
 
-_re_mouse_event = re.compile("^" + re.escape("\x1b[") + r"(<?[\d;]+[mM]|M...)\Z")
+_re_mouse_event = re.compile("^" + re.escape("\x1b[") + r"(<?[-\d;]+[mM]|M...)\Z")
 _re_terminal_mode_response = re.compile(
     "^" + re.escape("\x1b[") + r"\?(?P<mode_id>\d+);(?P<setting_parameter>\d)\$y"
 )
@@ -50,7 +50,7 @@
 
 
 class XTermParser(Parser[Message]):
-    _re_sgr_mouse = re.compile(r"\x1b\[<(\d+);(\d+);(\d+)([Mm])")
+    _re_sgr_mouse = re.compile(r"\x1b\[<(\d+);(-?\d+);(-?\d+)([Mm])")
 
     def __init__(self, debug: bool = False) -> None:
         self.last_x = 0.0