Phyllobates vittatus is a small frog, with males reaching 26 mm in SVL and females measuring up to 31 mm in SVL.
The back and head are generally solid black, although in some individuals there is an interrupted yellow median dorsal stripe. A wide gold, red-orange or orange stripe runs from each side of the snout over the eyes and back, down to the base of the thigh. A single white line goes from the shoulder and runs along the lip to just under the eye. The dorsal surfaces of the limbs show dense blue-green speckling on a black background, while the venter and ventral surfaces of the limbs are marbled with white or pale blue-green on black.