Cell-cell communication within any given tissue is an important aspect of correct organ function. The islets of Langerhans forming the endocrine pancreas are composed of alpha-, beta-, delta-, epsilon- and PP-cells, and interactions between these cells are required for fine-tuning glucose homeostasis of the body. The endocrine cells communicate through homotypic or heterotypic cell-cell adhesion, or in a paracrine fashion, and this communication is involved in the regulated secretion of islet hormones. This review discusses how islet hormones, secreted molecules and ions influence the endocrine cells and how cell adhesion molecules such as neural cell adhesion molecule, cadherins, connexin-36, Eph receptors and ephrin ligands, as well as extracellular matrix proteins, modulate pancreatic islet function.