This experiment was designed to study the toxic effects of cottonseed meal in Japanese quails.  A total of 84 male Japanese quails (Coturnix japonica) of 40 days of age were randomly divided into seven equal groups (A to G). Group A was fed on control diet, while three isonitric and isocaloric experimental feeds prepared by replacing soybean meal with varying proportions of cottonseed meal (CSM) were offered to groups B and C (13% CSM), D and E (27% CSM) and F and G (41% CSM). Feeds of groups C, E and G were also supplemented with 0.065, 0.135 and 0.205% ferrous sulphate, respectively. Duration of experiment was 42 days. Frequency of mounting, crowing and presence of foamy droppings were lower in groups receiving high percentage of CSM. Body weights of groups D and F were significantly lower, while addition of ferrous sulphate in feed rendered this difference non-significant, in groups E and G. Relative weights of liver and kidneys were significantly higher in group F  compared to  control group. A non significant difference was seen in feed intake among all the groups throughout the experiment. At 21 days, serum albumin was significantly lower in groups B, C and G compared to control. At 21 days, significantly lower serum total proteins was observed in groups B, C, D, E and G  compared to control. Seminiferous tubules of all CSM fed groups had necrotic cells, characterized by dark and small pyknotic nuclei among round spermatids in some tubules. Liver of groups B, C, D and E had cytoplasmic vacoulation of hepatocytes and newly formed bile ducts.  Supplementation of ferrous sulphate in experimental feeds partially ameliorated the effects of cottonseed meal on body weight, testes weight, feed intake and clinical signs.