For many years, organophosphate (OP) pesticides have been considered an attractive choice for pest control around the world. Excessive use of OPs is a concerning issue for human health. Although the genotoxic effect of these pesticides has been reported, studies that examined their aneuploidy-inducing effect are limited or absent. Therefore, we sought to investigate the potential of OP pesticides, which are extensively used in the Gaza Strip, to induce aneuploidy in human peripheral blood lymphocyte (PBL) cultures. To achieve this goal, we first assessed the cytotoxic effect of selected concentrations of Nemacur (fenamiphos), Rogor (dimethoate), and Dursban (chlorpyrifos) on human PBL cultures by the MTT assay. Then, fluorescence in situ hybridization (FISH) technique was used to determine the frequency of induced aneuploidy (chromosome loss or gain) in human PBL cultures treated with different concentrations of the three types of OPs. We found that all the OPs treatments used did not show appreciable cytotoxic effects. Increase in frequencies of aneuploidy, chromosome loss, and chromosome gain were observed after each treatment as compared to the results of their respective solvent control cultures, and that increase of aneuploidy was significantly evident at 0.050 mg/ml of Nemacur. It was also noticed that chromosome loss is more frequent than chromosome gain for each concentration of the three types of OPs. While the aneuploidy induction effect of the investigated OPs is not significant (except for the 0.050 mg/ml of Nemacur), these pesticides should be examined further since many people are exposed to them.