The present study was performed to investigate the immunomodulatory and health promoting effects of combined or singular administration of apple cider vinegar (ACV) and Lactobacillus casei in common carp (Cyprinus carpio) diet. An 8-week feeding trial was designed with following treatments: Control (basal diet), Pro (contains 107 CFU g−1L. casei), LACV (contains 1% ACV), HACV (contains 2% ACV), Pro + LACV (contains 107 CFU g−1L. casei plus 1% ACV) and Pro + HACV (contains 107 CFU g−1L. casei plus 2% ACV). Evaluation of skin mucus revealed notable increase of total Ig level and lysozyme activity in Pro + LACV and Pro + HACV treatments compared other groups (P < 0.05). Similarly, serum total Ig and lysozyme activity in HACV, Pro + LACV and Pro + HACV fed carps was remarkably higher than other groups (P < 0.05). However, regarding serum alternative complement (ACH50) activity significant difference was observed just between Pro + HACV and control treatment (P < 0.05). The highest expression of immune related (LYZ, TNF-alpha, IL1b, IL8) and antioxidant enzymes genes (GSR, GST) were observed in carps fed Pro + HACV and Pro + LACV. The expression of GH gene expression in Pro, LACV and HACV treatments was significantly higher than those in control group (P < 0.05). The highest expression level of GH and IGF1 was observed in fish fed combined Pro and ACV (P < 0.05). These results indicated that co-administration of ACV boosted immunomodulatory and health promoting effects of L. casei and can be considered as a promising immunostimulants in early stage of common carp culture.