Enrofloxacin evoked a dose-dependant stimulatory effect on the isolated intestinal smooth muscles of catfish. The drug potentiated the effect of acetylcholine on the isolated catfish epiaxial muscle. Moreover, enrofloxacin exerted a negative inotropic and chronotropic activities on the isolated catfish heart. Furthermore, the drug significantly increased the acetylcholine concentrations in the isolated intestinal preparations of catfish. The previous responses were proved to be due to an anticholine-estrase activity of the drug. Catfish treated with enrofloxacin elicited a significant decrease in serum calcium and alpha₂, globulins levels with a significant increase in phosphorus, triiodothyronine and thyroxine levels. In conclusion. enrofloxacin displayed an anticholine-estrase activity and evoked a significant decrease in serum calcium, alpha₂, globulin with elevated phosphorus, tri-iodothyronine and thyroxine levels in catfish.