In this paper, it was aimed to evaluate the effectiveness of four different types of filler materials with particle sizes below 63 mu m in sustainable geopolymer mortars. For this purpose, 25%, 50%, and 75% limestone powder (LSP), basalt powder (BP), waste marble powder (WMP), and recycled aggregate powder (RAP) were substituted with river sand and 13 different mixtures including reference were obtained. Metakaolin was used as the main binder material, and sodium hydroxide/sodium silicate was used in a ratio of 1:2 as an activator. In addition, blast furnace slag was added to the mixture as a reaction accelerator at a rate of 13% of the amount of metakaolin. To determine the mechanical properties of the produced geopolymer mortars, compressive strength, flexural strength, splitting strength, porosity, ultrasonic pulse velocity (UPV), and abrasion tests were performed. Also, SEM and XRD analyses were performed to examine the microstructures of the specimens. The satisfactory results obtained proved that all four types of filler materials can be used in metakaolin-based geopolymer mortars. Optimum rates for limestone powder, basalt powder, waste marble powder, and recycled aggregate powder were obtained as 50%, 50%, 25%, and 25%, respectively.