Organophosphate pesticides (OPPs) are widely used in agriculture and are associated with metabolic dysregulation and cognitive impairment. Emerging evidence links OPP exposure to insulin resistance and diabetes mellitus, a condition known to negatively impact brain function. Prior investigations in our laboratory identified significant dysregulation of arachidonic acid (AA) metabolites associated with the endocannabinoid system in both diabetic patients and those with chronic OPP exposure, with a marked reduction in serum AA levels in the OPP-exposed cohort. This study investigates the impact of OPP exposure and pre-diabetes on the hippocampal proteome and whether AA supplementation can mitigate the resulting neuronal proteomic alterations. Using a controlled rat model, high-resolution LC-MS/MS-based proteomics identified differentially expressed proteins across experimental groups. Both OPP exposure and pre-diabetes were associated with increased cognitive impairment and were associated with overlapping disruptions in pathways related to insulin resistance, mitochondrial function, synaptic plasticity, and neuronal development. AA supplementation mitigated cognitive decline and stabilized synaptic and metabolic proteins; however, residual pathway dysregulation highlights the complexity of these stressors. Our results reveal novel molecular intersections between environmental and metabolic drivers of cognitive impairment, establishing a rationale for further research into inexpensive, protective dietary interventions.