A photocatalyst composite film comprising cellulose acetate (CA)-supported bismuth ferrite (CA-BFO) was successfully fabricated using a phase-inversion technique. The composite was used to assess the removal efficiency for a mixture of crystal violet (CV) and indigo carmine (IC) dyes under direct sunlight. The effects of pH, amount of adsorbent, initial dye concentration, and contact time were investigated. The results indicated that the optimum pH for the removal of both cationic and anionic dyes was 6.0. The best catalyst loading of 0.04 g/L of BiFeO₃ distributed in the cellulose acetate membrane could degrade up to 100 ppm of mixed dyes and remain efficient over a wide pH range. The results were consistent with those of single dye removal, with the composite exhibiting preferential adsorption to anionic dyes, IC and having a higher photocatalytic affinity for cationic dyes, CV. Thus, a synergistic mode of CV and IC dye removal by adsorption and photodegradation was proposed. Moreover, the composite approach is a promising alternative for the co-existence of cationic and anionic dye removal from wastewater because of its high efficiency and separation convenience.