Introduction: Youth-friendly sexual and reproductive health (SRH) interventions are essential for the health of adolescents (10–19 years). Co-designing is a participatory approach to research, allowing for collaboration with academic and non-academic stakeholders in intervention development. Participatory action research (PAR) involves stakeholders throughout the planning, action, observation, and reflection stages of research. Current knowledge indicates that co-producing SRH interventions with adolescents increases a feeling of ownership, setting the scene for intervention adoption in implementation settings. Objectives: This scoping review aims to understand the extent of adolescents’ participation in PAR steps for co-designed SRH interventions, including the barriers and facilitators in co-designing of SRH intervention, as well as its effectiveness on adolescents’ SRH outcomes. Methods: Database searching of PubMed, Medline, Embase, CINAHL, Scopus, Web of Science, Google Scholar, and organisational websites was performed, identifying 439 studies. Results: Upon screening, 30 studies (published between 2006–2021) met the inclusion criteria. The synthesis identified that adolescents were involved in the planning and action stages of the interventions, but not in the observation and reflection stages. Although the review identified the barriers and facilitators for co-designing SRF interventions, none of the included studies reported on the effectiveness of co-designing SRH interventions with adolescents; therefore, meta-analysis was not performed. Conclusions: While no specific outcome of the interventions was reported, all papers agreed that adolescent co-designing in ASRH interventions should occur at all stages to increase understanding of local perceptions and develop a successful intervention.