Toxic pollutants containing Cr(VI) are unavoidable in industrial production. Photoreduction is commonly performed during the removal of Cr(VI) by reducing Cr(VI) to Cr(III). In this work, polydopamine/Ag-nanoparticles (PDA/AgNPs) were synthesized under mild conditions through the self-polymerization of PDA and the in situ reduction of Ag⁺ to Ag nanoparticles via PDA. The relevant structural characterizations were confirmed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The electrochemical characterizations were performed through photoluminescence (PL) spectroscopy and electrochemical impedance spectroscopy (EIS) performance. PDA/AgNPs-2 (2.5 mg) catalysts showed outstanding catalytic ability with a 98% removal ratio after 60 min illumination. Unique adhesion behavior and the good electrical conductivity of PDA/AgNPs led to the excellent removal performance of Cr(VI) via absorption and photo-induced reduction. The PDA/AgNPs were acceptably reused after 7 cycles. This work provides a feasible reference to synthesize photocatalyst materials for removing hazardous Cr(VI).