The effects of food-simulating liquids (FSLs) on the microhardness and surface roughness: Luna (LN, conventional nanohybrid), Aura Bulk Fill (AB, bulk-fill composite), and Stela Automix (SA, self-cured composite) were evaluated. The materials were exposed to air as control, artificial saliva and three FSLs: 50% ethanol-water solution, 0.02N citric acid, and heptane-over different time intervals to compare their performance. Microhardness and surface roughness were measured at baseline, seven days, and 30 days after immersion. Two-way ANOVA revealed significant interactions between FSLs and materials for both microhardness and surface roughness (p<0.001). All materials showed a decrease in microhardness and an increase in surface roughness over time, except when exposed to air. LN exhibited the highest microhardness and lowest surface roughness, while SA demonstrated the lowest microhardness and the highest surface roughness in all FSLs. SA's surface roughness decreased in citric acid, potentially due to its lower filler content, which may result in a less durable surface. Ethanol and citric acid had the most detrimental effects on the microhardness of all materials, while heptane caused the most significant surface roughness changes in SA. These results highlight the material-specific responses to FSLs, with important implications for material selection and restoration longevity in clinical practice.