Fish processing sector produces huge amounts of high organic load wastewater. The use of primary-stage treatments such as the coagulation/ flocculation process (C/F) reduces part of the organic load, improving subsequent stages of wastewater treatment. Aiming at a primary wastewater treatment, the present study evaluated the performance of a combined coagulation/flocculation process, using two different coagulants (natural and inorganic) with and without an auxiliary copolymer, to treat the fish processing industry wastewater analyzing to the physicochemical parameters of water quality. For this purpose, the optimal conditions of the C/F process were obtained from a Doehlert experimental design (DED), using as independent variables the concentration of coagulants (Tanfloc SH or FeCl 3 ) and copolymer (Zetag®) and as the response variables the color and turbidity removals (%). The results show color, turbidity, chemical oxygen demand and biochemical oxygen demand removals that range between 92 and 97% using both treatments at the FeCl 3 and copolymer concentration of 48.13 mg L −1 and 2.21 mg L −1 , respectively, and Tanfloc SH and copolymer concentration of 144.35 mg L −1 and 1.49 mg L −1 , respectively. C/F results were considered satisfactory due to the parameters' high initial values in the raw effluent. The treated effluent presented good biodegradability, and as C/F is a primary wastewater treatment, a subsequent biological treatment is needed so that the effluent meets the discharge standards. Tanfloc SH presented a removal efficiency comparable with the FeCl 3 at a primary wastewater treatment, having the advantage of a being biodegradable and nontoxic coagulant.