In order to evaluate the effects of supplementation of a low-protein wheat-based diet (WBD) with different levels of threonine on performance and immune function, 280 male one-day-old broiler chicks (Ross 308) were used in a completely randomized design in seven treatment groups of four replicates each. Treatments were a WBD supplemented with seven levels of threonine (90, 100, 110, 120, 130, 140, and 150% of NRC (1994) recommendation. During 1-21 d of age, feed intake (FI), body weight gain (BWG) and feed conversion ratio (FCR) were recorded weekly. For evaluation of immune system response, sheep red blood cells (SRBC) was injected; and in order to evaluate cutaneous basophil hypersensitivity (CBH) response, Phytohemagglutinin (PHA) (100 μ g) was injected into toe web. The mean of BWG significantly decreased when the threonine level increased to more than 130% NRC (1994) recommendations during 15-21 days of age (P<0. 05). Adjusting threonine level at 110% NRC (1994) recommendations comparing to 90%, improved FCR during 15 to 21 and 1 to 21 d of age (P<0. 05). Supplementation of the WBD with threonine at the levels of 110, 120, and 130% of NRC (1994) recommendation, significantly increased antibody titre against SRBC (P<0. 05). Higher dietary threonine levels (110% and 130% of NRC (1994) recommendations), increased CBH response after PHA injection (P<0. 05). Overall, it seems that the requirements of threonine in WBD for optimum performance and immune system enhancement, is more than the NRC (1994) recommendations.