Synaptotagmin (Syt) triggers Ca2+-dependent membrane fusion during secretion via its tandem C2 domains, termed C2A and C2B. The seventeen known human isoforms are active in different secretory cell types, including neurons (SytI and others) and pancreatic β cells (SytVII and others). Here, quantitative fluorescence measurements reveal notable differences in the membrane docking affinities, kinetics, and molecular driving forces for C2A and C2B domains from SytI and SytVII, using vesicles comprised of physiological target lipid mixtures. In agreement with previous studies, the Ca2+ sensitivity of membrane binding is greater for both domains from SytVII than for their counterparts in SytI. We demonstrate that for C2A, this increased sensitivity is due to a stronger SytVIIC2A membrane interaction, which involves substantial contribution from the hydrophobic effect. Association and dissociation rate constants for both SytVII domains are found to be significantly slower than their counterparts in SytI. For SytVIIC2A, the dissociation rate constant is ∼50-fold slower than SytIC2A and is reminiscent of the cPLA2C2 domain that is known to insert deeply into membranes. Addition of sodium sulfate decreases the dissociation rate of SytVIIC2A but not SytIC2A, further indicating that hydrophobic contacts play a major role in SytVIIC2A membrane docking. Thus, SytVIIC2A docks to membranes via both hydrophobic and electrostatic interactions, while the membrane docking interaction of SytIC2A is predominantly electrostatic. The inclusion of phosphatidylinositol-4,5-bisphosphate (PIP2) in membrane mixtures leads to increased affinity and slower dissociation for both C2B domains, but has minimal effects on C2A domains. Overall, highly homologous domains from these two proteins exhibit distinct mechanisms of membrane binding that may reflect their functions in different cell types.