Rainbow trout (Oncorhynchus mykiss) were examined effects of apricot kernel oil (Prunus armeniaca L.) on the immune mechanisms. After Fish weight 40 ±0,03 g was intraperitoneal (i.p.) injection 1% and 10% apricot kernel oil (AKO), blood was taken from the caudal vein of anesthetized (50 ppm, benzocaine) fish. Myeloperoxidase production (MPO), Serum bactericidal activity, protein levels, Lysozyme response (LYS) and total immunoglobulin (Ig) were determined on days 3, 7, 14 and 21. The same strategy was conducted on a control bunch. No contrasts were found within the levels of immunuglobulin between the control and test groups. However, there were considerable increases in bactericidal activity, MPO, LYS, protein levels and important differences were detected between the control and experimental groups. AKO can be utilized to improve the resistant instruments of rainbow trout.