The study objective was to evaluate the effects of fennel seeds (Foeniculum vulgare) as a dietary additive on some behaviors, fear response, performance, carcass traits, serum metabolites and economic efficiency of male fayoumi chickens. For this purpose, 60 birds of 28 days of age were divided into control group and three treatment groups. Each group (5 birds x 3 replicates). The fennel seeds were added to the treatment diets at concentrations of 0.4, 0.8, and 1.2%, respectively. Result showed that, fennel seeds treated groups had significant difference (P<0.05), and showed higher feed intake, ingestive and comfort behavior, production efficiency index, body weight, weight gain, relative economic efficiency, serum total protein and globulin. While, had lower aggressive behavior and fear response than birds on fennel free diet. On the other hand, no changes in feed conversion, relative growth rate, dressing percentage and internal organ relative weight, serum calcium and phosphorus levels due to fennel addition. It could be concluded, that fennel seeds have a growth stimulatory effect, improving behavior, fear response, economic efficiency and general health