Ostracism-being ignored and excluded-is part of many individuals' daily lives. Yet, ostracism is often studied in laboratory settings and rarely in natural settings. Here, we report one of the first investigations into ostracism in everyday life by documenting how often and where ostracism occurs; who the sources of ostracism are; and how ostracism affects targets' feelings and behaviors. Two experience sampling studies using event-contingent (N = 323, k = 1,107 ostracism experiences in 14 days) and time-signaling sampling approaches (N = 272, k = 7,943 assessments including 767 ostracism experiences in 7 days) show that ostracism is an aversive experience that takes place in a range of contexts and relationships, as often as two to three times per week on average. Reconciling previously mixed findings regarding ostracism's effects on behavior and extending existing theory, we propose a novel framework of behavioral reactions based on need-threat levels: When psychological needs are severely threatened, individuals react to everyday ostracism with avoidance (i.e., withdrawal) and antisocial inclinations (i.e., they exhibit significantly stronger antisocial intentions, although they do not engage in antisocial behavior more frequently). Conversely, when psychological needs are threatened to a lesser extent, individuals are more likely to adopt approach behaviors (i.e., prosocial behavior, talking to others, or connecting with them on social media). Our findings considerably extend present theorizing in ostracism research as they allow to understand when and how individuals experience everyday ostracism and how behavioral reactions after ostracism form in real life. (PsycInfo Database Record (c) 2024 APA, all rights reserved).