A depth-adjustable electrical box assembly for mounting of a fan or fixture on a ceiling including a fan/fixture box and a depth adjustment screw that is always accessible for adjusting the depth of the electrical box with respect to the ceiling. Bracket mounting screws are held captive with the assembly. A slide plate on the fan/fixture box is slideable with respect to the box. A base plate integral with the slide plate includes apertures therein for accepting the bracket mounting screws. A screw retainer, held securely to the fan/fixture box by a bracket, retains the end of the adjustment with respect to the box. Straps on the slide plate provide threaded engagement with the depth adjustment screw and enables the slide plate to slide with respect to the electrical box in response to rotation of the adjustment screw.