The promotion of prosocial behavior is a remarkable MDMA property. Such an effect is rather uncommon among other psychoactive substances and has been proposed to be of relevance for the potential therapeutic utility of MDMA. We aim to expand our knowledge of the prosocial effects of MDMA, considering sex and housing conditions as extra variables. To this end, housed individually or collectively, male and female Wistar rats were tested using the Social Preference paradigm. Contrary to expectations, MDMA treatment reduced the prosocial behavior in male rats, irrespective of the housing conditions. Similar effects are observed in female rats, but only in those individually housed. Intriguingly, no MDMA social effects were observed on those female rats, which are collectively housed. Also interesting was the apparent existence of two subgroups of rats that responded differentially to the MDMA administration, suggesting that individual variations among rats may influence the degree of their response to the MDMA treatment. More work is needed to understand how differences across individuals are relevant to the behavioral effects of MDMA.