The expression and organization of the phototransduction signaling proteins into a specialized light-sensing organelle, the rhabdomere, is required for photoreceptor cells to detect light. We report the characterization of the mutant Pph13(hazy). Pph13 is a homeodomain transcription factor expressed only in photoreceptor cells. Pph13 expression correlates with the differentiation and not specification of photoreceptor cells. In agreement with its expression profile, we find Pph13 is required for both rhabdomere morphogenesis and for the proper detection of light. In addition, we demonstrate that Pph13 exerts its effect by the regulation of photoreceptor specific gene expression.