A reversible electrical box assembly for mounting an electrical fixture on a ceiling. The electrical box assembly includes a hollow body having a sidewall. The sidewall includes two ends and a center. A flange extends outwards from the sidewall at a location offset from the center thereby dividing the sidewall into a long and short sidewall. A panel is provided for closing either of the ends of the hollow body. The panel can be secured to either the long sidewall or to the short sidewall to create an opposing sidewall of an appropriate length for extending through the ceiling covering at the job site.