Introduction: This study introduces the first German Open Scale of Social Information Processing (GOSSIP) and evaluates its psychometric properties. Even though social information processing (SIP) and its important role in developmental psychopathology is a rising field of interest, model-based standardized assessment tools are still scarce. Methods: GOSSIP was developed to assess SI processes in boys and girls aged eight to 21 years. First, 61 vignettes (combinations of pictures and short written descriptions of the situation depicted) were evaluated by an expert group and piloted with 48 healthy participants (aged 8–21). The best-rated vignettes were then implemented in a Web-based application. 191 participants completed GOSSIP. Of those, 76 answered additional questionnaires to assess their social skills and psychopathology. Internal consistencies for the emotional and cognitive GOSSIP scales were determined. Latent profile analysis (LPA) was used to identify subgroups of children and adolescents characterized by specific SIP profiles (i.e., patterns of emotional, cognitive, and behavioral responses to the GOSSIP). Furthermore, the external validity of the participants’ attribution tendencies in GOSSIP was evaluated in real life by smartphone-based Ecological Momentary Assessments (EMA). Results: The internal consistencies for the emotional and cognitive scales (angry, ashamed, physical aggression, pro-social response, revenge, and outcome expectancy) were good to excellent. The scales of hostile interpretation, relation aggression, sadness, and exclusion showed borderline/acceptable internal consistency. Correlation analysis confirmed convergent validity with self-reported social skills and external validity with ratings of aggressive and pro-social behaviors. The LPA revealed three profiles as the best fit of the data. The first group is named “aggressors,” the second “social-emotional group,” and a third named “ashamed-internalizing group.” However, no significant association was found between the attribution tendencies derived from GOSSIP and EMA data. Discussion/Conclusion: GOSSIP is the first model-based German Web-based assessment for several SIP mechanisms that showed overall adequate psychometric properties. GOSSIP can be used to classify individuals into SIP profiles that differ in terms of their cognitive and emotional response tendencies and therefore could contribute to the development of targeted interventions. Integrating assessments of emotional responses into GOSSIP revealed an important role of “shame” in SIP and the development of psychopathology. Furthermore, the lack of external validity between GOSSIP and EMA calls into question how attribution tendencies are best assessed in future studies.