The effects of four different levels of wood betony (WB) (Stachys lavandulifolia Vahl) extract (0, 2, 4 and 8% W/W in the diet) were investigated on some serum enzymatic activities and acute stress response of juvenile common carp (Cyprinus carpio). After 10 weeks post feeding, two groups of fish (0 and 8% WB) were subjected to handling and crowding stress and the stress responses including serum cortisol, glucose and some electrolytes (Na+, K+ and Ca+2) levels were assayed. The results revealed that the fish fed on 8% WB had significantly lower levels of lactate dehydrogenase (LDH) and alanine transaminase (ALT) compared to the control group (P<0.05). Although cortisol and glucose levels were increased significantly shortly after stress (P<0.05), the elevation level was significantly lower for fish fed on 8% WB (P < 0.05). In control group, sodium level decreased (P < 0.05) at 3 h post stress but did not show any change in 8% WB (P > 0.05). The potassium and calcium levels showed insignificant fluctuations post stress (P>0.05). Dietary inclusion of WB seems to improve liver function and response to acute stress in juvenile common carp.