This study aims to investigate the workability, visual appearance and mass loss, compressive, and flexural strength properties of the single and hybrid glass (GL) and basalt (BA) fiber added fly ash (FA)-based geopolymer cement (GPC) mortars after the high-temperature effect. Micro- and macro - GL and BA fibers were added to the GPC mixtures in two different volumetric ratios, 0.5% and 1%. 300, 500, and 800 ◦C of high temperatures were applied to the GPC mortar samples. After the high-temperature effect, microstructural variations of selected GPC mortar specimens were determined using scanning electron microscope (SEM) analysis tests. As a result of the study, it was seen that the use of GL and BA fiber had a very negative effect on the workability of the mixtures and caused a significant decrease in the spreading diameters. Compared to the control concrete, it was observed that the GPC samples with GL and BA fiber additives had considerably higher (upper 5%) residual compressive and flexural strengths after the high-temperature effect. Furthermore, the hybrid use of GL and BA fibers is somewhat more effective than single GL and BA fibers in increasing the residual compressive and flexural strengths of the GPC mortar samples after the effect of high temperature. In addition, since GL fibers are less agglomerated and exhibit a more homogeneous distribution in blends, they are slightly more effective in improving both workability and residual compressive and flexural strengths of GPC mortar samples compared to BA fibers.