Testosterone (T) plays a crucial role in regulating male sexual function acting at central as well as at peripheral level. However, its contribution depends on the phase of sexual response considered. Several brain areas express androgen receptors (ARs), and T is often considered the main hormonal determinant of sexual desire. Accordingly, testosterone replacement therapy can ameliorate reduced sexual desire in hypogonadal subjects, independently of the severity of erectile dysfunction (ED). Conversely, the contribution of T accounted in the regulation of erectile function is more controversial. Preclinical and clinical evidence supports an involvement of T in maintaining penile architecture and functioning. However, the T role on erection is rather modest, since the ARs not only control penile pathways favoring erection but also those resulting in its ending. Finally, T supports orgasm and ejaculation phases by playing trophic activity on accessory glands and favoring contractile activity of the male genitalia tract. In conclusion, available data substantiate that T in male adulthood is mainly involved in the synchronization of sexual desire with a timely regulated erection and orgasm.