Testosterone exerts a profound influence on mood, behavior, and overall quality of life in men. These effects stem from both endogenous testosterone levels and its external administration via testosterone replacement therapy (TRT). The interplay between testosterone and these psychological and behavioral dimensions is shaped, in part, by genetic factors such as the CAG repeat polymorphism in the androgen receptor gene. Although not all findings are consistent, substantial evidence suggests that a deficiency of serum testosterone, namely hypogonadism, has a significant impact on psychological traits in men. Importantly, these deficits may be ameliorated through TRT, restoring well-being and enhancing quality of life. Ultimately, testosterone plays a pivotal role in shaping the emotional and social dimensions of men’s lives.