A system for filling a vehicular electrochromic rearview mirror reflective element includes a filling crucible, a compressible sealing element, and a fixture configured to support an unfilled mirror cell. The filling crucible includes a fluid reservoir, a mirror cell receiving portion and a channel between the fluid reservoir and the mirror element receiving portion. The mirror cell receiving portion of the filling crucible is shaped to receive a perimeter portion of the unfilled mirror cell therein such that the fill port of the unfilled mirror cell is aligned with the channel of the filling crucible. With the unfilled mirror cell supported at the fixture, the mirror cell receiving portion of the filling crucible receives the upper perimeter portion of the unfilled mirror cell with the compressible sealing element between the filling crucible and the unfilled mirror cell. The mirror cell is filled under negative pressure.