This paper investigates the effect of graphene on the properties of slag and fly ash-based ambient cured geopolymer paste and mortar. Graphene was added with five percentage (0.0%, 0.1%, 0.5%, 1.0% and 1.5%) of aluminosilicate materials by weight. The initial and final setting times of geopolymer pastes were reduced. The workability of geopolymer paste and mortar was slightly decreased with graphene. The 7-day and 28-day compressive strength of geopolymer mortar with 1.0% addition of graphene increased by 25% and 10%, respectively. The addition of 1% graphene could be considered as optimum proportion to improve the compressive strength of geopolymer mortar.