With advances in medical care, more youth with intellectual and/or developmental disabilities (IDD) are transitioning into adulthood. Patient- and family-centered, integrated care is warranted around this time of transition. Support teams (including the youth, caregivers, teachers, and pediatricians) should engage in transition planning, ideally starting between 12 and 14 years of age, to identify and develop resources to support the maturing youth’s capacity for independent decision-making. Care teams should consider the varied levels of alternative decision-making support, which may include supported decision-making, medical proxy decision-making, power of attorney, and/or establishment of legal guardianship arrangements, to support the youth’s health and well-being optimally. Ultimately, if independent decision-making is not appropriate, the goal for youth with IDD should be the least restrictive alternative, while preserving human rights and human dignity and promoting their autonomy. These considerations review alternative decision-making support, concepts, and legal requirements available for youth with IDD and their care teams. Pediatricians can support youth with IDD and their families in the transition process and decision-making autonomy by actively engaging the youth in care decisions, supporting needs for augmentative communication, fostering their expression of preferences and understanding of care decisions, and linking them to resources such as the medical-legal partnership model.