Pesticides along with with their degradation products spread throughout the environment and contaminate the water, leading to a consequent potential risk to humans and also the environment. The study aims to determinene the residual pesticides (organophosphorus, pyrethroids ), herbicides, and fungicides in the water resources (wells, deep wells, springs, spring-heads, and flumes) of Kermanshah Province, Iran. Water samples were taken from 50 stations from April to June 2016, and analyses were performed using gas-chromatography–mass-spectrometry techniques. Data were analysed using SPSS version 20. One of the most important points of this study is the fact that all water resources were safe except for deep wells. Total concentration of organophosphorus was 2.2 ppb. The mean concentration of pyrethroids in Islamabad Gharb and Songhor was 0.574 and 2.235 ppb, respectively. Organophosphorus and pyrethroid pesticides total concentration was more than the European standard. The contamination range of difenoconazole fungicide was 0.024 ppb (Gilan Gharb) and 1.089 ppb (Kermanshah). Glyphosate herbicide was only seen in Islamabad Gharb (0.011 ppb). The mean concentration of all pesticides in the investigated wells was more than the European standard. Estimating pesticide concentration is important for preserving aquatic ecosystems and human health.