Vulcanization, by creating a three-dimensional cross-linked network, improves the physicalmechanical and thermal properties of elastomers. A popular agent for curing natural rubber (NR) is sulfur. Insoluble sulfur (IS) and rhombic sulfur (RS) are common allotropes of elemental sulfur. In this research, it was observed that the use of the two types of sulfur (IS and RS) gives different results. In terms of cure behavior, tear resistance and hardness, RS-vulcanized NR performed better, whereas in viscosity, tensile strength, aging and compression set, IS-vulcanized NR was better; because of the lack of blooming, IS could replace of rhombic sulfur as the curing agent in certain applications.