Purpose: To compare the surface hardness of monochrome (single shade) and conventional composite resins after exposure to food-simulating liquids. Materials and methods: A total of 50 disk-shaped specimens of composite resin (n = 25 estelite alpha and n = 25 omnichroma) were fabricated in split teflon mold (15 mm diameter, 2 mm thickness). The specimens were divided into subgroups (n = 5/subgroup). The first subgroup acted as the control and incubated dry at 37 ± 0.5°C in darkness for 1 week. Each specimen of the other four subgroups was immersed separately into a tightly closed glass test tube with 2 mL of each solution of the four different food-simulating liquids (artificial saliva, citric acid 0.02%, heptane 50%, and 50% ethanol) and incubated at 37± 0.5°C in darkness, with daily manual agitation for 1 week. Vickers hardness number (VHN) was then measured for each specimen under a load of 0.49N and a dwell time of 15 seconds. The unpaired t-test was used to compare the two groups, while comparisons between >2 groups were performed using analysis of variance (ANOVA) with multiple comparisons post hoc Tukey test. Results: Omnichroma showed significantly higher Vickers hardness values in each storage condition than estelite alpha. Both omnichroma and estelilte alpha showed a reduction in the Vickers microhardness values in different solutions when compared to the dry condition. One-way ANOVA showed a significant difference (p < 0.001) between the subgroups of both composites. Estelilte alpha showed the greatest reduction in the Vickers microhardness values in the dry condition (21.94 ± 0.54 kgf/mm²) and the least value (15.92 ± 0.65 kgf/mm²) when immersed in 50% ethanol. Omnichroma also showed the greatest Vickers microhardness values in the dry condition (28.04 ± 0.99 kgf/mm²) and the least after immersion in 50% ethanol (21.90 ± 0.63 kgf/mm²). Conclusion: The 50% ethanol was the most critical food-simulating liquid, causing degradation in both composites. The resin formulation of urethane dimethacrylate/triethylene glycol dimethacrylate (UDMA/TEGDMA) of monochromatic composite showed better stability in surface hardness properties after exposure to different food-simulating liquids. The inclusion of prepolymerized filler in the nanohybrid composite had a negative impact on the surface hardness.