Background: Assets-based approaches are well-suited to youth living in majority world contexts, such as East Africa. However, positive psychology research with African adolescents is rare. One hindering factor is the lack of translated measures for conducting research. Objective: This study builds capacity for positive youth development research in East Africa and beyond by examining a Swahili measure of youth development that assess both internal and external strengths. Methods: We translated a well-researched and internationally used measure of assets, [Developmental Assets Profile (DAP), along with measures of self-efficacy, ethnic identity, sense of community, and community participation] into Swahili. Psychometric results for 1241 diverse Tanzanian young people were evaluated. Open-ended asset listing and focus groups provide complementary data and identify areas for further investigation. Results: Most scales displayed promising internal consistencies and were related to each other and to socio-demographics. Moreover, the DAP predicted self-efficacy and vulnerability status. Exploratory factor analysis supported a three-factor structure of the DAP. Test-retest reliability and language equivalency scores yielded less satisfactory results. Qualitative data support the assets approach and suggests areas for consideration based on culture and context. Conclusions: The developmental assets framework and Swahili measure may be used to advance research in this understudied, yet important region. Adolescents in Africa should be included in international efforts to develop PYD theory and to understand the diverse contexts in which youth develop and contribute.