In light of the increasing global population of young people, practitioners and policy makers face formidable challenges in promoting positive youth development and the successful transition to adulthood. Youth participatory research is one promising and rapidly growing approach for generating evidence to inform policy and intervention strategies to best serve youth populations. Here, we consider how developmental science contributes to our understanding about the benefits--for youth, as well as for programs and policies--of engaging youth at different developmental stages in research. We link insights from developmental science to evidence from youth-engaged research to determine where the most fruitful developmental matches may occur. We can maximize the benefits for youth and simultaneously improve research projects when developmental needs, capacities, priorities, and constraints of youth in various stages are thoughtfully considered.