The feasibility of utilizing fish scales as a new biosorbent for removal of textile dyes, namely crystal violet (CV) and methylene blue (MB), from their aqueous solutions was investigated in a batch system. Experiments were conducted as a function of initial solution pH (2–10), contact time (0–180 min), biosorbent dose (0.5–5 g) and temperature (293–313 K). The Langmuir isotherm model showed excellent fit to the equilibrium biosorption data of both CV and MB. The maximum dye biosorption capacity of fish scale was calculated as 74.39 and 58.67 mg g−1 for CV and MB, respectively, at 313 K. Biosorption phenomena of CV and MB by fish scales followed pseudo-second-order kinetics. Activation energy calculated by using the Arrhenius equation suggested the chemisorption nature of the biosorption processes. A thermodynamic assessment indicated the spontaneous and endothermic nature of biosorption of the textile dyes. It could be concluded that fish scales may be used as an inexpensive and effective biosorbent for removal of dyes from aqueous solutions.