Significance Cell surface proteins are regulated by a constant cycle of internalization and recycling from intracellular compartments called endosomes. From these organelles, two protein sorting platforms, sorting nexin 27 (SNX27) and the retromer complex, play a critical role in the retrieval of various proteins responsible for ion transport, glucose metabolism, neurotransmission, and other cell functions. Based on the three-dimensional structure of SNX27 in complex with the retromer subunit VPS26, we define the mechanism by which these proteins cooperate to drive endosomal cargo sorting. Retromer and SNX27 dysfunction is implicated in various disorders, including diabetes, Down syndrome, Parkinson disease, and Alzheimer’s disease, and this work provides important insights into the assembly of this essential endosomal sorting machinery.