Medicinal plants are increasingly used in aquaculture owing to their beneficial impacts onthe health status of farmed fish. The current study was conducted to investigate the effect of nutmeg(Myristica fragrans) extract on growth, immunity, antioxidant parameters, and resistance of commoncarp (Cyprinus carpio) againstAeromonas hydrophila. In addition,in vitroantibacterial activity of theskin mucus of fish fed on nutmeg extract was evaluated against three major fish pathogenic bacteriathrough the standard disk diffusion method. Fish (17.27±0.11 g) were divided into four groupsand fed on experimental diets containing different levels of nutmeg extract, including zero (control),0.5% (M1), 1% (M2), and 2% (M3) per kg diet. Results showed that nutmeg significantly enhancedgrowth parameters after a four-week feeding trial. Feed conversion ratio was remarkably reducedwith the lowest value reported for the M3 group, whereas weight gain was notably increased in M2and M3. No significant effect was found on the hematological profile, including mean corpuscularhemoglobin concentration, mean corpuscular hemoglobin, mean corpuscular volume, and hematocrit,while the highest levels of red blood cells and white blood cells were found in the M3 group. Stressbiomarkers, including glucose and cortisol, were the lowest in the M3 group. Serum and skin mucusimmunological and antioxidant parameters were significantly higher in M3, followed by M2, wherethe highest resistance was also observed. In addition, skin mucus samples effectively inhibitedStreptococcus iniae,Yersinia ruckeri, andAeromonas hydrophila. Overall, the present results suggestthat dietary nutmeg (20 g/kg diet) could be used as a growth promotor and immunostimulant incommon carp.