Objectives: The purpose of this study was to evaluate the effect of simulated gastric acid on surface roughness of monolithic ceramics. Materials and methods: A total of forty ceramic disk-shape were obtained from different four ceramic materials (10 each). Each disk was sawed with a final thickness of 1.0 mm using Isomet saw from ceramic blocks of each material (Ceramil Zolid fx white {Z}, IPS e.max CAD {E} HT A3, Vita Suprinity {S} HT A3, and Cerasmart {C} HT A3). Ceramil Zolid fx white disks were colored with A3 coloring liquid and sintered, while e.max CAD and Vita Suprinity were crystallized according to manufacturer's instruction. The surface roughness of ceramic disks was measured with a stylus profilometer before and after immersion in simulated gastric acid (HCl) for 96 h at 37 °C incubator. The collected data were statistically analyzed using ANOVA followed by Tukey's post-hoc test and the significance level was set at P ≤ 0.05. Results: There was no statistically significant difference (P ˃ 0.05) for Z and E groups after acid immersion, while for S and C groups, there was a statistically significant difference (P ˂ 0.05) after acid immersion. Conclusion: Surface roughness increased significantly for Vita Suprinity and Cerasmart after gastric acid immersion, while decreased for Zolid fx and IPS e.max CAD but not significantly.