Subgroup formation within larger virtual teams can lead to biased information sharing and conflict. Given this, the present study examined how social categories (i.e., in-group vs. out-group status) and interpersonal behaviors (i.e., a teammate behaving positively vs. negatively) influenced intentions and attitudes toward subgrouping in short-term virtual teams. One hundred sixty-four participants interacted in four-person teams using a synchronous chat program. The analysis showed that, though both social categories and interpersonal behaviors affected subgrouping choices, interpersonal behaviors had a stronger effect. Additionally, there was no evidence for the "black sheep hypothesis" predicting that in-group members behaving negatively discourages subgrouping. Overall, this exemplified how minimal categorical cues trigger in-group favoritism and out-group discrimination in virtual teams as anticipated by social identity models. The findings also illustrated how interpersonal behaviors robustly affect virtual team dynamics as stated by social information processing theory.