Stress-related hormonal imbalances can negatively affect puberty and reproductive function. The aim of our study was to investigate whether administration of a GABA agonist (phenibut) or vitamin E during puberty could prevent long-term effects of chronic immobilization stress on oxidative status and sexual behavior in adult male rat. Adolescent male rats were subjected to daily 1-hour immobilization from postnatal day 30 to 45. Experimental animals received phenibut (100 mg/kg) or vitamin E (50 mg/kg) per os, 30 min- utes before each stress session. At six months of age, the animals were assessed for male sexual behavior in the presence of a receptive ovariectomized female primed with estradiol diacetate and progesterone. Serum testosterone levels were measured, and malondialdehyde and diene conjugate (DC) contents were determined in testes as markers of lipid peroxidation (LPO). Stressed rats showed increased sexual activ- ity and copulative capacity. Phenibut administration normalized the number of intromissions but caused a twofold reduction in serum testosterone and significantly elevated testicular LPO products. In contrast, vitamin E reduced the latency to first ejaculation without affecting testosterone levels. Although DC levels were elevated, overall LPO remained unchanged. In conclusion, the use of a GABA agonist (phenibut) in adolescent male rat has a moderate preventive effect on stress-induced alterations in sexual behavior, while vitamin E did not demonstrate such an effect. Additionally, phenibut induced oxidative stress in the gonads and significantly suppressed serum testosterone levels. These findings highlight long-term effects of phenibut use and underscore the need for caution when prescribing it to adolescents for the treatment or prevention of anxiety-neurotic condition.