The major platelet integrin αIIbβ3 is the main receptor involved in platelet functions such as aggregation and spreading on extracellular matrix. Like all other integrins, αIIbβ3 is capable of transducing signals both from inside and outside of the cell. To mediate these functions, αIIbβ3 interacts with intracellular and transmembrane proteins. The identification of these proteins, as well as the study of their functions, has provided valuable insights into integrin-mediated function and signaling. This review summarizes the known proteins that directly interact with αIIbβ3 and provides an overview of their roles in integrin function.