Passive sampling is a sampling technique for the monitoring of organic micropollutants such as pesticides in the aquatic environment. This technique allows the determination of time-weighted average (TWA) concentrations, providing first, prior determination of the sampling rates (Rs) of all target micropollutants via laboratory calibration, and second, a possible correction for in situ application, depending on the micropollutant and the experimental conditions. Indeed, flow rate, temperature and the concentration of dissolved organic carbon (DOC) in water may have an impact on the accumulation kinetics of micropollutants in passive samplers, and may imply biased TWA concentrations. Recently, we developed the passive stir bar sorptive extraction (SBSE) for the determination of moderately hydrophobic to hydrophobic pesticides in freshwaters. In the present laboratory work, we studied the impact of flow rate, temperature and the concentration of DOC on the accumulation kinetics of 20 pesticides in SBSE stir bars. Eight experiments were conducted simultaneously according to a full factorial experimental design. Results showed, for hydrophobic pesticides, significant effects of the factors on the accumulation kinetics. These experiments allow identifying pesticides whose accumulation rate depends on experimental conditions and which PRC might best correct the laboratory sampling rates.