Varicoceles are dilated veins within the spermatic cord and a relatively common occurrence in men. Fortunately, the large majority of men are asymptomatic, however, a proportion of men with varicoceles can suffer from infertility and testosterone deficiency. Sperm and testosterone are produced within the testis, and any alteration to the testicular environment can negatively affect the cells responsible for these processes. The negative impact of varicoceles on testicular function occurs mainly due to increased oxidative stress within the testicular parenchyma which is thought to be caused by scrotal hyperthermia, testicular hypoxia, and blood-testis barrier disruption. Management of varicoceles involves ligation or percutaneous embolization of the dilated veins. Repair of varicoceles can improve semen parameters and fertility, along with serum testosterone concentration. In this review, we discuss the pathophysiology of varicoceles, their impact on testicular function, and management.