Microplastics (MPs) can alter pesticide migration in soils by modifying soil structure and influencing pesticide sorption and transport. Freeze–thaw cycles (FTCs), which are common in temperate regions, naturally change soil structure and may influence the environmental fate of both MPs and pesticides. We investigated a mixture of 20 pesticides with a broad range of physical-chemical properties in a factorial column experiment combining sandy and loamy soils, room-temperature and FTC treatments, and the presence or absence of 1% (w/w) polyethylene (PE) particles (63–100 μm). Transport was characterized by the pore volumes required to reach 5% and 50% of the nominal influent concentration (BV₅ and BV₅₀). FTCs reduced mean breakthrough volumes by approximately 15–35% in sandy soil and 40–85% in loamy soil, whereas PE addition generally increased breakthrough volumes by approximately 7–17% across treatments. Loamy soil showed greater pesticide retention at room temperature and a 1–2.5-fold stronger response to FTCs than sandy soil. Associations with organic-carbon partition coefficients (K_OC) and water solubility (S_w) indicated compound-dependent transport. Changes in soil physical properties and complementary experiments with selected triazines suggested possible physical and partitioning-related contributions, particularly in loamy soil, consistent with FTC-induced changes in soil structure and flow pathways.