A vehicular rearview mirror assembly includes a mirror head having a mirror casing and an electro-optic mirror reflective element. A mirror casing sidewall has a terminal end region that circumscribes an open end of the mirror casing and has a rounded end region surface. A first substrate of the reflective element has a rounded circumferential perimeter region extending at least partially between a front surface and a rear surface of the first substrate and having a first radius of curvature. The rounded surface of the mirror casing has a second radius of curvature. The substrate thickness of the first substrate is less than the first radius of curvature. The rounded surface of the mirror casing and the rounded circumferential perimeter region of the first substrate combine to provide a curved transition between the front surface and the outer surface of the mirror casing.