Water pollution has becoming an increasingly serious issue, and it has attracted a significant amount of attention from scholars. Here, in order remove heavy metal hexavalent chromium (Cr (VI)) from wastewater, graphitic carbon nitride (g-C 3 N 4 ) was modified with molybdenum disulfide (MoS 2 ) at different mass ratios via an ultrasonic method to synthesize g-C 3 N 4 /MoS 2 (CNM) nanocomposites as photocatalysts. The nanocomposites displayed efficient photocatalytic removal of toxic hexavalent chromium (Cr (VI)) from water under UV, solar, and visible light irradiation. The CNM composite with a 1:2 g-C 3 N 4 to MoS 2 ratio achieved optimal 91% Cr (VI) removal efficiency at an initial 20 mg/L Cr (VI) concentration and pH 3 after 120 min visible light irradiation. The results showed a high pH range and good recycling stability. The g-C 3 N 4 /MoS 2 nanocomposites exhibited higher performance compared to pure g-C 3 N 4 due to the narrowed band gap of the Z-scheme heterojunction structure and effective separation of photo-generated electron-hole pairs, as evidenced by structural and optical characterization. Overall, the ultrasonic synthesis of g-C 3 N 4 /MoS 2 photocatalysts shows promise as an efficient technique for enhancing heavy metal wastewater remediation under solar and visible light.