Teratozoospermia (ejaculation of <40% morphologically normal sperm) commonly occurs within the Felidae, including certain domestic cats, but the cellular and molecular mechanisms that give rise to this phenomenon remain unknown. This study quantified spermatogenesis to identify differential dysfunctions in teratospermic versus normospermic (>60% normal sperm/ejaculate) domestic cats. Sperm used were from electroejaculates and cauda epididymides. Testes from 10 normo- and 10 teratospermic males were obtained by castration and then evaluated by histomorphometry, flow cytometry, and testicular testosterone enzyme immunoassay. Some morphometric traits (tubular diameter, epithelium height, interstitial area, number of Leydig cells, and blood vessels per cross-section) as well as testicular testosterone concentrations were similar between groups, but testicular volume was greater in teratospermic males. Stage frequencies differed also between both cat populations, suggesting possible dysfunctions in spermiation. Quantification of cell populations in most frequent stages revealed more spermatogenic cells and fewer Sertoli cells per tubule cross-section as well as per tissue unit in teratospermic donors. Hence, the ratio of spermatogenic cells per Sertoli cell was elevated in the teratospermic cat. DNA flow cytometry confirmed higher total spermatogenic and meiotic transformations in teratospermic males. In summary, compared with normospermic counterparts, teratospermic cats have a higher sperm output achieved by more sperm-producing tissue, more germ cells per Sertoli cell, and reduced germ cell loss during spermatogenesis. Gains in sperm quantity are produced at the expense of sperm quality.