The advent of pesticide production on large scale has contributed immensely to the quality and quantity of agricultural products, and averting diseases that stem from pest vectors. Despite these benefits, inappropriate or excessive usage of these chemicals could have negative impacts on humans and other organisms in the environment. Thus, this study was designed to detect and quantify fenobucarb and chlorbenside in wastewater and lake water samples by a gas chromatograph system coupled to a mass selective detector. A suitable temperature program was used to elute the two analytes at distinct retention times, and satisfactory system performance values were obtained under optimum conditions. All standard solutions and spiked samples were gravimetrically prepared in order to enhance the accuracy of quantification. The analytes were not detected in the two test samples, but spike recovery experiments were performed to validate the accuracy of the method. Percent recoveries calculated using the external calibration method were below 75%. Thus, matrix matching calibration method was used to mitigate matrix effects to obtain approximately 100% recovery results for five different spike concentrations.