Actin polymerization often occurs at the plasma membrane to drive the protrusion of lamellipodia and filopodia at the leading edge of migrating cells. A role for actin polymerization in another cellular process that involves the reshaping of the plasma membrane — namely endocytosis — has recently been established. Live-cell imaging studies are shedding light on the order and timing of the molecular events and mechanisms of actin function during endocytosis.