The development of male germ cells from the primordial germ cell stage to that of the mature spermatozoon is a key time of epigenetic reprogramming. Orchestrated by specialized enzymes, DNA methylation and histone modifications undergo dynamic changes throughout gametogenesis. Alterations to any level of the sperm epigenetic coding may affect fertility and the sperm’s contribution to normal embryo development. In support of an important role for normal genomic methylation patterns in human sperm, a number of recent studies have reported abnormal DNA methylation in imprinted and other sequences in infertile men. As well, a number of genomic imprinting disorders in offspring, associated with underlying DNA methylation alterations in imprinted genes, have been linked with infertility and the use of assisted reproductive technologies (ARTs). In this chapter, we discuss different aspects of the sperm epigenome, from the timing and mechanisms underlying the acquisition of epigenetic patterns to the consequences of perturbing such patterns. The focus here is on DNA methylation, since it is not only one of the most well-studied epigenetic modifications taking place during male germ cell development but also one that has been clearly linked to infertility in men.