What predicts sociable behavior? While main effects of personality and situation characteristics on sociability are well established, there is little evidence for the existence of person-situation interaction effects within real-life social interactions. Moreover, previous research has focused on self-reported behavior ratings, and less is known about the partner's social perspective, i.e. how partners perceive and influence an actor's behavior. In the current research, we investigated predictors of sociable behavior in real-life social interactions across social perspectives, including person and situation main effects as well as person-situation interaction effects. In two experience-sampling studies (Study 1: N = 394, US, time-based; Study 2: N = 124, Germany, event-based), we assessed personality traits with self-and informant-reports, self-reported sociable behavior during real-life social interactions, and corresponding information on the situation (categorical situation classifications and dimensional ratings of situation characteristics). In Study 2, we additionally assessed interaction partner-reported actor behavior. Multilevel analyses provided evidence for main effects of personality and situation features, as well as small but consistent evidence for person-situation interaction effects. First, extraverts acted more sociable in general. Second, individuals behaved more sociable in low-effort/positive/low-duty situations (vs. high-effort/negative/high-duty situations). Third, the latter was particularly true for extraverts. Further specific interaction effects were found for the partner's social perspective. These results are discussed regarding their accordance with different behavioral models (e.g., Trait Activation Theory) and their transferability to other behavioral domains.