The aim of the study was to determine the effects of solid-state fermentation of cottonseed meal (FCSM) with Candida utilis on broiler growth performance and toxicity in comparison to unfermented cottonseed meal (CSM) or soyabean meal (SBM, control). In total 150 one-day-old male Cobb 400 broilers were randomly assigned to 3 dietary treatments with 5 replications of 10 birds each. Animals were fed control diet with SBM, diet with CSM : SBM (1:1) and diet with FCSM : SBM (1:1) until 21 day of life. Fermentation decreased free gossypol content in CSM from 583.40 to 191.70 mg · kg⁻¹, and degraded total gossypol from 5830.19 to 3882.91 mg · kg⁻¹ CSM. In comparison to the control diet, FCSM : SBM (1:1) diet did not affect (P > 0.05) the average daily growth and feed conversion ratio, while CSM : SBM (1:1) diet decreased (P < 0.05) these parameters. However, FCSM : SBM (1:1) diet, similarly to CSM : SBM (1:1) diet, increased (P < 0.05) the relative weight of liver and the serum activity of alanine aminotransferase, and decreased (P < 0.05) the relative weight of thymus in comparison to the control diet. In conclusion, residual gossypol or/and degradation products of gossypol in FCSM may still be hepatotoxic and immunotoxic for broilers when SBM is half-replaced by FCSM in diet (155 g · kg⁻¹), although the contents of free gossypol and total gossypol have been markedly reduced and no adverse effect on growth performance was observed.