We have constructed a theoretical model of endocytosis in yeast. Recent experiments on endocytosis in yeast demonstrate that the actin cytoskeleton plays a crucial role in the deformation of the cell membrane. However, competing ideas remain as to precisely how the actin cytoskeleton organizes itself to help drive the deformation. To begin to resolve this controversy, we mathematically model clathrin-mediated endocytosis in yeast using variational methods and Monte Carlo simulations. Our results also suggest that the pinch-off mechanism may be assisted by a pearling-like instability.