An eight?week research was conducted to investigate the effects of single or combined administration of sodium propionate (Na?P) and sodium acetate (Na?A) on the performance of yellowfin seabream (Acanthopagrus latus ) juveniles (6.5 ± 0.3 g). A plant protein (PP)?rich diet was supplemented with sole or blends of organic acid salts (OAS) namely Na?P and Na?A to design six experimental feeds including control (without OAS), Na?P5 (5 g/kg Na?P), Na?P10 (10 g/kg Na?P), Na?A5 (5 g/kg Na?A), Na?A10 (10 g/kg Na?A) and Na?P A (5 g/kg Na?P 5 g/kg Na?A). Except for Na?A5 group, the other OAS?supplemented treatments had higher growth and feed efficiency ratio than the control (p < .05). The inclusion of OAS in the experimental feeds pronouncedly enhanced plasma lysozyme and alternative complement pathway activities compared to the control. Furthermore, fish fed on the OAS?supplemented diets had greater catalase and glutathione peroxidase activities in the liver than the control (p < .05). Total antioxidant capacity in the liver of fish fed on the OAS?supplemented diet also was higher than the control. Fish fed on the OAS?supplemented diets had higher pepsin, trypsin and lipase activities than the control. The insulin?like growth factor 1 (IGF?1) gene expression was remarkably down?regulated in the liver of fish fed on the OAS?supplemented diets compared to the control especially in groups fed on the Na?P10 and Na?A10 diets. The greatest IGF?1 gene down?regulation level in the gut was in fish fed on the Na?P5 and Na?P10 diets. The interleukine?1? in the gut was remarkably up?regulated in the control compared to the other groups (p < .05). The lactic acid bacterial colonies count in the gut of the control was lower than the OAS?supplemented groups. Based on the findings of the present study, supplementing PP?rich diets with 10 g/kg Na?P or blends of Na?P (5 g/kg) and Na?A (5 g/kg) beneficially alleviated inflammatory responses and improved immune parameters and digestive capaci