This experiment was conducted to investigate the effects of increasing the level of dietary supplementation of vitamin E (VE) on production performance and biochemical characteristics of cloacal foam in male Japanese quail (Coturnix coturnix japonica).A total of 225 male Japanese quail chicks (day old) were randomly distributed to three dietary treatments for a period of 30 weeks. Each treatment comprised of three replicates, each containing 25 chicks. The basal diet (T1) contained 12.30IUVEkg−1 and the two experimental diets were supplemented with 150 and 300IUVEkg–1 (diets T2 and T3, respectively). dl-α-Tocopherol acetate was used as the source of VE. All chicks were provided feed and water ad libitum.Mean body weights, feed intake, feed conversion ratio (FCR) and mortality of the birds in the different treatment groups showed no significant differences (P>0.05), whereas a significant (P<0.05) increase (29.81 and 50.83%) in average foam weight was evident in the VE-treated groups (T2) compared with control (T1) and T3 groups. The biochemical characteristics of foam, in terms of quantities of protein and nitric oxide (NO), did not differ significantly (P>0.05), whereas the quantities of glucose (60.01%) and acid phosphatase (ACP, 32.46%) were significantly (P<0.05) higher in the T3 group. By contrast, the quantities of alkaline phosphatase (ALP), glutamic oxaloacetic transaminase (GOT) and glutamic pyruvic transaminase (GPT) were significantly (P<0.05) lower (48.84%, 10.38% and 22.08%, respectively) in the T3 group and higher in the T1 (control) and T2 groups.From this study, it can be concluded that dietary supplementation of VE to the basal diet has no effect on the production performance but supplementation of a higher level of VE (300IUkg–1diet) improved the biochemical characteristics of the foam and moderate levels of VE (150IUkg–1diet) improved the foam production of male Japanese quail.