What predicts sociable behavior? While main effects of personality and situation characteristics on sociability are well established, the determinants of sociable behavior within real-life social interactions are understudied. Moreover, although such effects are often hypothesized, there is to date little evidence of person-situation interaction effects. Finally, previous research focused on self-reported behavior ratings, and less is known on 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 interaction, and corresponding information on the situation (dimensional ratings of situation characteristics and categorical situation classifications). In Study 2, we additionally assessed interaction partner-reported behavior. Multilevel analyses provided consistent evidence for main effects of personality and situation features, and for person-situation interaction effects. First, extraverts acted more sociable in general. Second, individuals behaved more sociable in hedonic/positive/low-duty situations (vs. eudaimonic/negative/high-duty situations). Third, the latter was particularly true for extraverts. Further specific interaction effects were found for the other social perspectives. These results are discussed regarding the complex interplay of persons and situations in shaping human behavior.