ABSTRACT The use of saline effluents from fish farming in agricultural activities has been increasing, especially in semiarid regions. This study was to evaluate the use of saline effluents from fish farming for the irrigation of Croton blanchetianus and to analyze the physiological and biochemical responses. After the cuttings were planted, irrigation with the effluent began. Treatments included four salinity levels (control, 1.5, 2.5, 3.5 dS m-1). The control treatment was the supply water (0.56 dS m-1). The evaluated variables were growth, relative water content, dry biomass, and levels of proteins, proline, hydrogen peroxide, malondialdehyde, and photosynthetic pigments. Physiological and biochemical adjustments ensured the maintenance of relative water content and osmotic adjustment under saline conditions without increasing lipid peroxidation. The salinity levels did not affect C. blanchetianus, indicating the lack of saline stress. The fish farm effluents are rich in organic matter, from food, and excrement, which was beneficial for the development of C. blanchetianus. The reuse of saline effluents from fish farming for the irrigation of C. blanchetianus can be a viable environmental alternative, avoiding direct disposal into the environment.