Human mitochondrial DNA (mtDNA) is 16.6 kb in size and resides in the mitochondrion. It encodes 13 of the subunits of the electron transfer chain that generates the vast majority of cellular ATP through the process of oxidative phosphorylation (OXPHOS). The importance of OXPHOS to sperm motility and function has been controversial. However, we present a case for the importance of OXPHOS in sperm function based on the effects that pathogenic mtDNA mutations and deletions have on sperm motility and function and how they are descriptive of certain forms of male subfertility. We also describe patterns of inheritance for the mitochondrial genome and how the elimination of sperm mtDNA in mammals prevents the transmission of mutant/deleted mtDNA to subsequent generations but when there is leakage it leads to a severe phenotype. This is also portrayed in the light of how mtDNA copy is reduced during the later stages of spermatogenesis and how reduced mtDNA copy number in the mature spermatozoa is indicative of good-quality, not poor-quality spermatozoa.