The curing behavior and microstructure of natural rubber/silica foams were studied. Error function-based and autocatalytic models were correlated with the curing characteristics data of samples. The incorporation of silica into natural rubber caused an increase in the foam density and decrease in the cell size. Moreover, by increasing the curing temperature, cell size became larger and cell size distribution became non-uniform. It was thought that the higher temperature of foaming limited the bubble growth due to faster curing reaction. Lower viscosity and lower strength of rubber at high temperature increased the cell coalescence resulting in larger cell size and non-uniform cell distribution.