Tunisian populations of Culex pipiens pipiens, an important vector of human diseases, have developed resistance to organophosphate insecticides. To understand the origin of this resistance, knowledge of the impact on agricultural pest and mosquito control activities and its significance for the resistance mechanisms will be required. Five populations of C. p. pipiens were collected at various sites with different agricultural pest and mosquito control activities throughout Tunisia and tested for fenitrothion resistance level. Results were compared to those obtained from a control population where no chemical activities have been carried out. Our results strongly suggest the presence of a correlation between agrochemical products and the recorded resistance despite a rather limited number of studied sites (five populations). On the other hand, organophosphates control activities let us suggest the existence of an important impact on fenitrothion resistance. However, it appears that the application of pyrethroids have little to no impact on fenitrothion (organophosphate) resistance. The recorded resistance of the control population should be due to anthropogenic factors; however, the combined effect of migration and gene flow on the evolution of insecticide resistance should also be taken into consideration. The recorded resistance was mediated by both enzymatic detoxification and target-site sensitivity. Our findings showed a positive correlation between both metabolic and target site resistance and the level of resistance. In conclusions, we can say that the use of pesticides and insecticides by both agricultural and public health departments in Tunisia should be more rationalized to reduce the development of resistance in C. p. pipiens populations.