Given the frequency of cases resolved by guilty pleas, associated legal and collateral consequences, and developmental factors relevant to both youth and young adults that may impact psycholegal abilities, a growing body of research has explored plea understanding and decision making in these populations. This scoping review was conducted to map the literature in this area to inform future research, practice, and policy. Specifically, this review explored what is known about current plea practices, theoretical conceptualizations, factors impacting plea understanding and decision making, and gaps in the literature. Four databases were searched (PsycNet, Web of Science, Criminal Justice Abstracts, Sociological Abstracts) for records mentioning both pleas and youth (ages 10–17) and/or young adults (ages 18–25), yielding 53 sources. Sources were primarily focused on youth, with a small subset involving young adults. Results indicated that very few studies have examined plea practices for youth; however, some identified concerns include barriers faced by defense lawyers, lack of consensus regarding caregiver involvement in the process, and systemic inequities that may constrain decision making, all of which warrant further study. Findings indicate that youth are at increased risk of poor understanding and decision making in the plea context due to their age, and this may extend into young adulthood. However, the impact of specific individual, psychosocial, and system-level factors remains understudied. In addition, little is known about how youth and young adults actually make plea decisions, or how existing theoretical conceptualizations of plea decision making apply to these groups. Implications for research, practice, and policy are discussed.