Abstract: Objective: To investigate the neurotoxic effects of deltamethrin (DM) on the neurobehavioral performance of mice subjected to different exposure durations. Methods: Thirty-two adult male C57BL/6J mice were randomly assigned into four groups, with eight animals in each group: 30-day control, 30-day DM, 90-day control, and 90-day DM groups. The DM groups received oral gavage of 4.5 mg/kg DM (1/20 of the LD50) for 30 days or 90 days, while the control groups were administered an equivalent volume of corn oil. Learning and memory capabilities of mice were assessed using the Morris water maze (MWM). Cortical histopathological changes of the mouse cortex were observed through hematoxylin and eosin (HE) staining and Nissl staining. The levels of glutathione (GSH), superoxide dismutase (SOD), catalase (CAT), and malondialdehyde (MDA) in the cortical tissue were measured. Results: In the MWM test, no significant differences were observed between the 30-day DM group and the control group（P＜0.05）. However, the 90-day DM group showed significant decreases in the time spent in the target quadrant, the distance traveled in the target quadrant, and the number of platform crossings compared to the control group (P＜0.01). The content of GSH in the cortical tissue of the 90-day DM group was lower than that of the control group (P＜0.05). The activity of SOD in the 30-day DM group was lower than that of the control group (P＜0.01), the 90-day DM group was lower than that of the control group (P＜0.01), and the activity of CAT in the 90-day DM group was also lower than that of the control group (P＜0.01). Conclusion: Different exposure durations of low doses of DM have adverse effects on the learning and memory capabilities and antioxidant capacity of adult male mice, with these effects intensifying over extended exposure durations. The potential impact of long-term, low-dose exposure to DM on neurobehavior should be taken into consideration.