The potential of Fe3O4 magnetic nanoparticles (MNPs) as efficient adsorbent for acid red 141, as anionic dye, from aqueous solutions was investigated. For this purpose, Fe3O4 MNPs were synthesized via chemical co-precipitation method. The synthesized MNPs were characterized by SEM, FT-IR, XRD, and EDX techniques. The various parameters affecting dye adsorption were investigated and optimized. The kinetic studies for acid red 141 adsorption showed rapid sorption dynamics by second-order kinetic model. Dye adsorption equilibrium data were fitted well to the Freundlich isotherm rather than Langmuir isotherm. The over all adsorption process was favorable, exothermic, and follows both intraparticle and Elovich diffusion models. Maximum capacity (qmax) was calculated, and was found to be 700 mg/g at 10°C and 985 mg/g at 50°C. The results showed that magnetic nanoparticles could be employed as a low-cost efficient adsorbent for removal of anionic dyes from aqueous solution.