Depression is a prevalent mental health disorder characterized by persistent sadness and a lack of interest in daily activities, often treated with pharmacological options such as selective serotonin reuptake inhibitors (SSRIs) and other antidepressants. However, these treatments can have limitations, including delayed efficacy and side effects. In this study, we hypothesized that pumpkin seed oil (PSO) exhibits antidepressant activity by modulating oxidative and neuroinflammatory pathways. This is the first study to report the antidepressant effect of PSO in the hippocampus. Unlike the traditional monoamine hypothesis for current antidepressants, the proposed mechanism for PSO is based on the inflammation theory. Sixty adult male rats were divided into six groups: the first group served as the control, while groups two and three received venlafaxine (20 mg/kg) or PSO (40 mg/kg), respectively. Groups four to six were subjected to chronic mild stress (CMS); group four remained untreated, while groups five and six received venlafaxine or PSO. CMS induced a redox imbalance, evidenced by elevated malondialdehyde and nitric oxide levels, and reduced activity of antioxidant enzymes (catalase, superoxide dismutase, and glutathione peroxidase) in the hippocampus. CMS also increased neuroinflammation, decreased neurotransmitter levels, and downregulated the expression of histamine-N-methyl transferase and tyrosine hydroxylase. These neurochemical changes were associated with behavioral alterations, including reduced sucrose preference, body weight loss, and coat state score, along with increased immobility time in the tail suspension test and freezing time in the open field test, and decreased rearing activity. Administration of PSO reversed all neurochemical and behavioral changes induced by CMS by attenuating oxidative stress and neuroinflammation. Notably, PSO demonstrated efficacy comparable to or better than venlafaxine in mitigating these effects.