<p>Oxidative stress plays a significant role in the progression of behavioral deficits associated with diabetes. Research has suggested that <i>Foeniculum vulgare</i> has anti-diabetic, antioxidant, anxiolytic, and antidepressant properties. This study aims to investigate the effects of treating streptozotocin (STZ)-induced diabetic male Wistar rats with a methanolic extract of <i>Foeniculum vulgare</i>, focusing on behavioral responses related to depression and anxiety and oxidative stress changes in the prefrontal cortex. Twenty-four adult male Wistar rats were randomly divided into four groups (<i>n</i> = 6 per group): a normal control group, an untreated diabetic control group, a diabetic group treated with 300 mg/kg of metformin, and a diabetic group treated with 250 mg/kg of methanolic extract of <i>Foeniculum vulgare</i> seed. Immediately upon confirmation of diabetes in the diabetic groups, all treatments were initiated and continued for 28 days. At the end of the treatment period, anxiety- and depression-related behaviors were evaluated using the open field test (OFT), the elevated plus maze (EPM), and the forced swimming test (FST). Catalase (CAT), nitric oxide (NO), and malondialdehyde (MDA) levels were measured in the prefrontal cortex. Additionally, we conducted a histological examination of the prefrontal cortex (PFC). Our findings indicated that diabetes elevated anxiety-like and depressive-like behaviors, decreased exploratory and locomotor activities, and increased oxidative stress in the prefrontal cortex. The treatment with 250 mg/kg of methanolic extract of <i>Foeniculum vulgare</i> reduced the STZ effect on behavioral disorders as observed in the OFT, EPM, and FST. Additionally, it restored the PFC, revealing normal-appearing pyramidal cells. These findings indicate that <i>Foeniculum vulgare</i> could be an effective option for preventing and treating behavioral complications related to diabetes by attenuating oxidative stress in PFC.</p>