Functioning as key players in cellular regulation of membrane curvature, BAR domain proteins bend bilayers and recruit interaction partners through poorly understood mechanisms. Using electron cryomicroscopy, we present reconstructions of full-length endophilin and its N-terminal N-BAR domain in their membrane-bound state. Endophilin lattices expose large areas of membrane surface and are held together by promiscuous interactions between endophilin's amphipathic N-terminal helices. Coarse-grained molecular dynamics simulations reveal that endophilin lattices are highly dynamic and that the N-terminal helices are required for formation of a stable and regular scaffold. Furthermore, endophilin accommodates different curvatures through a quantized addition or removal of endophilin dimers, which in some cases causes dimerization of endophilin's SH3 domains, suggesting that the spatial presentation of SH3 domains, rather than affinity, governs the recruitment of downstream interaction partners. Display omitted ► CryoEM structure of membrane-bound full-length N-BAR protein endophilin ► N-BAR lattices are fundamentally different than F-BAR lattices ► Nonspecific, weak, and antiparallel interaction between H0 helices stabilize lattice ► Some lattice geometries allow SH3-domain dimerization between adjacent N-BAR dimers Unlike other proteins in the membrane-remodeling BAR family, endophilin forms lattices that are held together by surprisingly nonspecific interactions, in which membrane curvature depends on the number of bound endophilin dimers rather than their orientation or conformation.