Depression and anxiety are common psychiatric disorders accounting for social and economic burdens. Previous studies have shown that oxidative stress and oxidant/antioxidant imbalance are involved in the pathophysiology of psychiatric disorders. Experiencing early-life adversities (like maternal separation [MS] stress) provoked psychiatric disorders. Trigonelline (TRG) is a pyridine alkaloid that has various pharmacological effects including hypoglycemic, neuroprotective and memory-improving properties. To investigate the antidepressant-and anxiolytic-like effects of TRG focusing oxidative stress, we applied the MS paradigm to male mice at postnatal day (PND) 2-14 (3 h daily, 9-12 a.m.) and investigated the behaviors at PND 45-47. Using valid behavioral tests including a forced swimming test (FST), splash test, open field test (OFT) and elevated plus maze (EPM), we investigated behavioral modifications. Additionally, we examined the effects of MS and TRG treatment on the level of malondialdehyde (MDA), nitric oxide (NO) and also antioxidant capacity in the brain and serum. Our results showed that MS provoked depressive-and anxiety-like behaviors in the FST, OFT, EPM and splash test, which are associated with an increase in MDA and NO levels as well as a decrease in antioxidant capacity in the brain and serum samples. Findings determined that TRG significantly reversed the negative effects of MS on behavior that is accompanied by a decrease in MDA and NO as well as an increase in antioxidant capacity. Findings of the present study showed that beneficial effects of TRG may be, at least partially, mediated via the reduction of oxidative stress and an increase of antioxidant capacity.