The aim of this study is to explore the effects of the herbicide glyphosate on serum paraoxonase (PON1) activity, high-density lipoprotein (HDL), and total antioxidant (TAS) and oxidant (TOS) levels in Kars Creek Transcaucasian Barbs (Capoeta capoeta [Guldenstaedt, 1773]). Twenty four Capoeta capoeta are chosen within a weight range of 200 to 240 grams and they are equally divided into 3 groups, namely Groups I, II, III. The fish placed in Group I are received aquatic environment while Groups II and III were kept in aquatic environments with a pH value of 7.4 in tanks to which 0,01 and 0,02 mg/L glyphosate (N-phosphonomethyl glycine 480 mg/L), respectively. It was found that groups II and III had significantly lower serum plasma PON1, HDL and TAS levels than the control group (Group I). On the other hand, serum TOS levels were found significantly elevated in Groups II and III, in comparison to the control group. In this work, significant changes were found in the serum paraoxonase activity, HDL, TAS and TOS levels of fishes living in environments added 0.01 and 0.02 mg/L glyphosate.