An animal’s social environment can influence individual physiological and reproductive status, which might have implications for the success of ex situ conservation programs. This study investigated the relationship between an individual’s position in the social hierarchy, body and antler size, testosterone concentration, and seminal traits in male pampas deer maintained in all-male groups. The study was performed in a semi-captive population in Uruguay during the rut. Data were collected over a 4 year period from 18 different males kept in five groups each of 4–7 adult males (2–7 y old). An index of individual hierarchical success (hierarchical index; HI) was determined based on agonistic interactions with other males within the group. Males positioned higher in the social hierarchy had larger antlers (p = 0.02). In three out of four groups, testosterone was positively correlated with HI (p < 0.0001). Semen vitality was negatively related to HI in three groups (p < 0.0001); however, a positive relationship was observed in another group (p < 0.0001). In conclusion, position in the social hierarchy of semi-captive male pampas deer was positively related to antler size, and in most groups negatively related to semen vitality.