Young adults with serious mental health conditions (SMHCs) often do not engage continuously with mental health services, and there are few engagement interventions designed for them. This qualitative study presents a blueprint for conceptualizing and developing an engagement intervention designed for young adults with SMHCs. The blueprint includes the following activities: (1) establishing a strong theoretical basis, (2) designing an initial manual based on previous research and practice, (3) systematically examining feedback on the manual from stakeholders, and (4) examining the feasibility, acceptability, and implementation demands of the intervention. Interviews, group discussions, and journaling were utilized to collect information from young adult participant-researchers, intervention facilitators (i.e., recovery role models and clinicians), and additional stakeholders (e.g., clinic staff and administrators) (N = 43). Analyses were performed with multiple coders using constant comparative methods. Results revealed critical information to improve the intervention, while also suggesting that the engagement intervention for young adults with SMHCs has promise.