Oxytocin (OT) modulates adult mammalian sexual behavior, sperm production and transport, and steroidogenesis; however, the consequences of developmental manipulations of oxytocin have received little attention. The purpose of this experiment was to determine whether neonatal exposure to OT, an oxytocin antagonist (OTA), saline (SAL), or handling (HAN)-only would have long-term effects on reproductive potential in male prairie voles (Microtus ochrogaster). Adult males were observed for 24 h with a sexually receptive female and sexual behavior was recorded. Females were subsequently lavaged and smears were examined for sperm. Reproductive parameters including motility of epididymal sperm, testis weight, and plasma androgen levels were in the normal range. OT-treated males that did not mate within the first 30 min did not mate at all, and in comparison to controls, a higher proportion of those OT-treated and OTA-treated males that did mate did not transfer sperm to the females. OTA-treated males also had significantly higher testicular sperm concentrations than HAN-only males, and significantly lower epididymal sperm concentrations. These differences suggest that in males, developmental manipulations of OT may have the potential to influence the subsequent expression of sexual behavior and sperm transport.