An illuminating sign includes a base panel; an illuminating unit, and a front casing. The front casing includes a metallic light blocking frame attached on the base panel for enhancing a strength of the front casing, wherein the light blocking frame has a plurality of through slots spacedly formed thereon, a plurality of illuminating members securely supported in front of the base panel, and a highlighting element provided at the illuminating members, wherein when the illumination unit is operated for generating the light towards the front casing, the metallic light blocking frame not only blocks the light passing therethrough but also facilitates efficient and effective heat transfer from the illuminating unit to an exterior of the front casing for preventing the illuminating unit from being overheat within the front casing.