Abstract: To investigate the effects of L-carnitine and CoQ10 (CoQ) supplementation on performance and immune functions in ascites-susceptible broilers. L-carnitine supplemental levels were 0, 75, 150 mg/kg, CoQ supplemental levels were 0 and 40 mg/kg, respectively. Four hundred and eighty 1 day-old Arbor Acre male broiler chicks were randomly allocated into 12 groups with 5 replicates each, 8 birds per replicate. The results showed that performance was not significantly influenced by Lcarnitine and CoQ supplementation alone, but heart index of broilers was significantly increased during 0-3 week (P＜0.05),and the development of immune crgans was not significantly affeded.PCV was significantly decreased by L-carnitine supplementation alone (P<0.05), and was not affected by CoQ supplementation alone AHI and ascites mortality were decreased by L-carnitine, CoQ supplementation alone, and L-carnitine + CoQ supplementation together (P<0.05). Serum IgG content was improved by Lcarnitine supplementation alone (P<0.05), and was not affected by CoQ supplementatim alone and L-carnitine+CoQ supplementatim together. Lysozyme activity was increased by L-carnitine + CoQ supplementation together (P<0.05). Supplemental CoQ alone and L-carnitine + CoQ together decreased the peripheral blood lymphocyte (PBL) proliferation in response to concanavalin A (ConA) (P<0.05). The study suggested that the reduction of broilers′ susceptibility to ascites might be relevant with L-carnitine + CoQ supplementation’s improving some immune functions of broilers.