Chemistry and Chemical Processes Technologies Department, Vocational School of Tunceli, Munzur University, 62000 Tunceli, Turkey Rare Earth Elements Research and Application Center, Munzur University, 62000 Tunceli, Turkey E-mail: yelizipek@munzur.edu.tr Manuscript received online 16 October 2020, revised and accepted 28 November 2020 Glutaraldehyde (GA) is a famous cross-linker that is used for immobilization of enzyme or biologic material on electrochemical biosensor electrodes. It has an important role in pesticide biosensor studies. Because of the inhibitor effect of pesticides on acetylcholine esterase enzyme (AChE), it is generally immobilized on the electrode by cross-linking method. Glutaraldehyde is used as cross-linker agent to immobilize the enzyme on the electrode surface. Acetylcholine esterase activity is inhibited by pesticides or other neurotoxic compounds. This inhibition helps us to detect the pesticide residual. Although numerous electrochemical pesticide biosensors are based on generally the immobilization of the enzyme in the literature, an enzymeless biosensor based on GA has been developed in this study for the first time. Enzyme biosensors have high cost and needs special storage conditions. In this study, glutaraldehyde detected the carbaryl pesticide as sensitive as an acetylcholine esterase enzyme biosensor. The biosensor electrode was constructed with coating GA on glassy carbon electrode (GCE). Thus, it is a simple, low cost and practical method for pesticide detection in the water samples with low detection limit of 5×10–9 mol L–1 .