One of the management problems in aquaculture is the negative impact of operational factors on fish health and welfare. In order not to adversely affect fish welfare, various anesthetic agents are applied in routine aquaculture operations. Alternative extracts are used as anesthetic agents in addition to traditional agents, which will minimally affect fish health. In this study, the hematological, biochemical, oxidative and histopathological ef-fects of chamomile oil on rainbow trout (Oncorhynchus mykiss) were evaluated as an herbal anesthetic. The focus is on the anesthetic effect of chamomile oil at concentrations of 100 mu L/L, 150 mu L/L and 200 mu L/L and its physiological findings on fish after anesthesia. Recovery time was significantly longer for 200 mu L/L, while in-duction time was longer for 100 mu L/L. Hematological parameters generally showed an increasing trend until the eighth hour and decreased to normal levels again at the sixteenth hour. The gill histology of the fish treated with 100 mu L/L chamomile oil contains low degradation similar to the control group. However, hyperplasia and epithelial lifting were observed especially in the 150 mu L/L group, and additional hypertrophy and necrosis symptoms were observed in the 200 mu L/L group. As antioxidant activity, catalase and glutathione peroxidase showed higher results in the 100 mu L/L group compared to the other groups and similar to the control. Although cortisol decreased for all groups at the first moment after anesthesia, it increased to normal levels in the 150 and 200 mu L/L groups at the fourth hour. In the 100 mu L/L group, the cortisol level could not reach the control level even at the eighth hour. As a result, even though chamomile oil at a concentration of 100 mu L/L causes a relatively high induction time, it has a lower adverse effect on fish health than other groups.