Avian broiler chickens (504, 1-day old) were randomly divided into 9 groups with 4 replicates per treatment, to investigate the influence of dietary Fe and vitamin A levels on production performance, immune competence, serum catalase activity, serum insulin concentration, and indicators of blood iron status such as haemoglobin concentration and red cell count. Supplemental levels were: 0, 30, and 60 mg iron/kg diet; 750, 1500, and 2700 IU vitamin A/kg diet. The results showed that the iron concentration in the basal diet was sufficient for nutritional requirements and that iron supplementation was not necessary. Dietary iron levels did not affected bodyweight gain and feed : gain (P > 0.05) during the whole period, but influenced serum insulin concentration significantly (P < 0.01), with serum insulin concentration reaching a peak for the treatment 60 mg iron/kg. The influence of dietary iron level on haemoglobin concentration and erythrocyte count was significant (P < 0.05) from 0 to 4 weeks, and on erythrocyte count from 5 to 7 weeks. Different supplemental levels of vitamin A did not influence production performance and serum antibody titre to Newcastle Disease Virus, but the influence on blood T lymphocyte levels was significant (P < 0.01). The treatment with 2700 IU vitamin A/kg resulted in lower feed : gain and higher blood T lymphocyte levels than other treatments. Dietary vitamin A levels influenced serum catalase activity significantly (P < 0.01). Catalase activity was the highest when vitamin A supplemental level was 2700 IU/kg. Dietary vitamin A levels significantly affected erythrocyte count (P < 0.01) but not haemoglobin concentration during the whole period. The interaction of iron and vitamin A significantly (P < 0.05) influenced bodyweight gain, serum antibody titre to Newcastle Disease Virus, and blood T lymphocyte levels. The interaction of iron and vitamin A significantly (P < 0.01) influenced serum catalase activity at the end of Week 7, haemoglobin concentration during the whole period, and erythrocyte count from 0 to 4 weeks.The haemoglobin concentration and erythrocyte count in the group with no Fe supplementation and 750 IU vitamin A/kg were lower than normal values. The complementary effect between iron and vitamin A improved haemoglobin concentration and erythrocyte count in broilers.