Recent evidence attests to the shortcomings of typical services for improving outcomes among emerging adults with serious mental health conditions (SMHCs). Researchers and providers have responded by developing new programs and interventions for meeting the unique needs of these young people. A significant number of these programs and interventions can be described as taking a positive developmental approach, which is informed by a combination of theoretical sources, including theories of positive development, self-determination, ecological systems, and social capital. To date, however, there has been no comprehensive theoretical statement describing how or why positive change should occur as a result of using a positive developmental approach when intervening with this population. The goal of this article is to propose a general model that “backfills” a theory behind what appears to be an effective and increasingly popular approach to improving outcomes among emerging adults with SMHCs.