Synaptojanin is a phosphoinositide phosphatase that plays a crucial role in synaptic vesicle recycling. The focus of this review is on the major direct interacting partners of synaptojanin with respect to recognition motifs in synaptojanin isoforms and splice variants. Those proteins that bind synaptojanin are mainly involved in endocytosis and function at the interface between actin and the endocytic machinery. Some interaction partners underline synaptojanin's emerging role in signaling and pathophysiological processes.Abbreviations: BMRS1, metastasis suppressor 1; CHO cells, Chinese hamster ovary cells; EGF, epidermal growth factor; Ins(1,4,5)P3, inositol 1,4,5-trisphosphate;Ins(1,3,4)P3, inositol 1,3,4-trisphosphate; Ins(1,3,4,5)P4, inositol 1,3,4,5-tetrakisphosphate; PKB, protein kinase B; PtdIns(4,5)P2, phosphatidylinositol 4,5-bisphosphate; PtdIns(3,4,5)P3, phosphatidylinositol 3,4,5-trisphosphate; PtdIns(3,5)P2, phosphatidylinositol 3,5-bisphosphate; PtdIns(3,4)P2, phosphatidylinositol 3,4-bisphosphate; PtdIns, phosphatidylinositol; PTEN, phosphatase and tensin homolog deleted on chromosome 10