Purpose: To compare the two-year clinical performance of high-viscosity glass ionomer (Hv-GIC) restorations in noncarious cervical lesions with nanohybrid composite restorations applied with a three-step etch-and-rinse adhesive (E&Ra/nanoC). Materials and Methods: One hundred thirty-four noncarious cervical lesions were included and assigned to two groups according to the split-mouth design. The cervical lesions in the experimental group were restored with an Hv-GIC (Equia, GC), while a nanohybrid composite (G-aenial, GC) with a three-step etch-and-rinse adhesive (Optibond FL, Kerr) was applied as the control. All tested restorative materials were used according to the manufacturers' instructions. Clinical evaluation was performed after one week, six months, one year, and two years using World Dental Federation criteria. Data were analyzed using Friedman's ANOVA and Mann-Whitney U-tests (α = 0.05). Results: After two years, Hv-GIC restorations had a retention rate of 91% in comparison to 100% for E&Ra/nanoC restorations. Significant differences existed between the two restorative materials solely with respect to the retention parameter after two years (p = 0.008). Conclusions: The two-year clinical performance of Hv-GIC was clinically acceptable. However, the retention of E&Ra/nanoC restorations was significantly better than that of Hv-GIC restorations after two years. Keywords: high-viscosity glass ionomer, noncarious cervical lesions, nanohybrid composite