diff --git a/apprise/plugins/matrix.py b/apprise/plugins/matrix.py
index 62f00706..b6d27b60 100644
--- a/apprise/plugins/matrix.py
+++ b/apprise/plugins/matrix.py
@@ -69,18 +69,19 @@ MATRIX_HTTP_ERROR_MAP = {
 
 # Matrix Room Syntax
 IS_ROOM_ALIAS = re.compile(
-    r"^\s*(#|%23)?(?P<room>[a-z0-9-]+)((:|%3A)"
-    r"(?P<home_server>[a-z0-9.-]+))?\s*$",
+    r"^\s*(#|%23)?(?P<room>[A-Za-z0-9._=-]+)((:|%3A)"
+    r"(?P<home_server>[A-Za-z0-9.-]+))?\s*$",
     re.I,
 )
 
 # Room ID MUST start with an exclamation to avoid ambiguity
 IS_ROOM_ID = re.compile(
-    r"^\s*(!|&#33;|%21)(?P<room>[a-z0-9-]+)((:|%3A)"
-    r"(?P<home_server>[a-z0-9.-]+))?\s*$",
+    r"^\s*(!|&#33;|%21)(?P<room>[A-Za-z0-9._=-]+)((:|%3A)"
+    r"(?P<home_server>[A-Za-z0-9.-]+))?\s*$",
     re.I,
 )
 
+
 # Matrix is_image check
 IS_IMAGE = re.compile(r"^image/.*", re.I)
 
@@ -254,7 +255,7 @@ class NotifyMatrix(NotifyBase):
             "target_room_alias": {
                 "name": _("Target Room Alias"),
                 "type": "string",
-                "prefix": "!",
+                "prefix": "#",
                 "map_to": "targets",
             },
             "targets": {
diff --git a/tests/test_plugin_matrix.py b/tests/test_plugin_matrix.py
index d8c4f763..e8630a94 100644
--- a/tests/test_plugin_matrix.py
+++ b/tests/test_plugin_matrix.py
@@ -912,6 +912,22 @@ def test_plugin_matrix_url_parsing():
     assert "#room2" in result["targets"]
     assert "#room3" in result["targets"]
 
+    # Mixed-case alias with underscore should parse
+    result = NotifyMatrix.parse_url(
+        "matrix://user:token@localhost?to=#Dev_Room:localhost"
+    )
+    assert isinstance(result, dict) is True
+    assert len(result["targets"]) == 1
+    assert "#Dev_Room:localhost" in result["targets"]
+
+    # Mixed-case room id with underscore should be accepted by _room_join
+    from apprise.plugins.matrix import IS_ROOM_ID  # local alias
+    nm = NotifyMatrix(host="localhost")
+    nm.access_token = "abc"   # simulate logged-in
+    nm.home_server = "localhost"
+    # this should NOT be rejected by the regex
+    assert IS_ROOM_ID.match("!Jm_LvU1nas_8KJPBmN9n:nginx.eu")
+
 
 @mock.patch("requests.put")
 @mock.patch("requests.get")