Synthetic multicellular systems hold promise as models for understanding natural development of biofilms and higher organisms and as tools for engineering complex multi-component metabolic pathways and materials. However, such efforts require tools to adhere cells into defined morphologies and patterns, and these tools are currently lacking. Here, we report a 100% genetically encoded synthetic platform for modular cell-cell adhesion in Escherichia coli, which provides control over multicellular self-assembly. Adhesive selectivity is provided by a library of outer membrane-displayed nanobodies and antigens with orthogonal intra-library specificities, while affinity is controlled by intrinsic adhesin affinity, competitive inhibition, and inducible expression. We demonstrate the resulting capabilities for quantitative rational design of well-defined morphologies and patterns through homophilic and heterophilic interactions, lattice-like self-assembly, phase separation, differential adhesion, and sequential layering. Compatible with synthetic biology standards, this adhesion toolbox will enable construction of high-level multicellular designs and shed light on the evolutionary transition to multicellularity. Display omitted •Orthogonal, composable adhesin library allows control over specificity and affinity•Adhesion is maintained during cell growth and division•Cultures form lattice-like, phase separation, and differential adhesion patterns•Compatibility with synthetic biology standards allows complex multicellular designs The development of a genetically encoded toolkit of surface-bound nanobodies and antigens in E. coli allows for precise manipulation of cell-cell adhesion and rational design of diverse self-assembled multicellular patterns and morphologies.