ObjectiveParticipation is one of the key goals of re/habilitative processes. Since participation impacts adolescents' social–emotional development and overall health, this goal is particularly important for them. However, to date, no German‐speaking self‐assessment tool for participation among adolescents is available. This study sought therefore to develop such a tool and to test its psychometric properties.MethodsBased on a preliminary qualitative study, we developed 133 items for a pilot version of the Social Participation Inventory (SPI). The SPI assesses the objective dimension (i.e., attendance) and the subjective dimension (i.e., involvement and satisfaction) of participation. To test the psychometric properties of the SPI, we conducted a quantitative cross‐sectional survey and applied the SPI to n = 151 adolescents with and without disabilities and/or chronic diseases.ResultsBy using principal component analyses, we examined the SPI's consistency and verified the theoretical considerations regarding the two components of participation (i.e., objective and subjective dimensions). Items that did not load sufficiently on components were removed after careful theoretical‐based consideration. The condensed version of the SPI consists of 39 items that assess participation and 18 items to assess the perceived importance of respective areas of life. The SPI shows very good overall reliability (Cronbach's α = .920) and good validity.ConclusionThis study provides a new psychometrically tested participation self‐assessment scale for adolescence with and without disabilities and/or chronic diseases. Further research is needed to re‐evaluate its psychometric properties and to evaluate the application of the SPI in clinical and scientific contexts.