AbstractObjectivesThis study compared the color stability, water sorption, and solubility of a giomer composite and two nanohybrid composite resins.Materials and MethodsDisc‐shaped specimens (1‐mm thickness × 15‐mm diameter) of a giomer (Beautifil II, Shofu, Kyoto, Japan) and two nanohybrid (Filtek Z550, 3M ESPE, St. Paul, MN, USA; Tetric N‐Ceram, Ivoclar Vivadent, Schaan, Liechtenstein) composites (N = 10) were prepared. Baseline color measurements were taken, and specimens were immersed in water for 28 days. Following immersion, color values were remeasured, and color‐change values (ΔE) were calculated. Water sorption and solubility were assessed by mass gain or loss after storage in water for 28 days. Data were analyzed with one‐way analysis of variance and Tukey's post‐hoc tests (p = 0.05). Pearson's correlation test was used to assess possible correlations between water sorption and solubility, water sorption and color stability, and solubility and color stability (p = 0.05).ResultsWater sorbtion (%) and color change (ΔE) varied significantly among groups, with Beautifil II exhibiting the highest values (p < 0.001). No statistically significant differences were observed in water solubility values among the groups (p = 0.661); however, a linear, positive correlation was detected between solubility and discoloration (r = 0.368, p = 0.046).ConclusionWater sorption and discoloration values of the giomer composite group were significantly higher than those of the nanohybrids tested.Clinical SignificanceThe high levels of water sorption and discoloration of giomer composites are likely to have an adverse effect on esthetic restorations.