Purpose: To evaluate the 24-month clinical performance of cervical restorations using a nanohybrid and a flowable resin composite with a one-step self-etching adhesive. Materials and Methods: Twenty-one patients with at least one pair of non-carious cervical lesions participated in this study. A total of 134 non-carious cervical lesions were restored (67 with a nanohybrid resin composite, Grandio; 67 with a flowable resin composite, Grandio Flow) using a one-step self-etching adhesive system, Futura Bond NR, by one dentist. The restorations were evaluated for retention, color match, marginal discoloration, marginal adaptation, surface texture, anatomic form, and secondary caries by two calibrated examiners at baseline and after 6, 12, and 24 months using modified USPHS criteria. The survival rates of the restorations were calculated by the Kaplan-Meier estimator. The comparison of resin composites for each category was performed with the Pearson chi-square test, and the performance of restorations at baseline and after each recall time was evaluated using McNemar's test (p 0.05). Results: All patients attended the 24-month recall. The retention rates at 6 months were 66% and 58%, and 61% and 57% at 12 months for Grandio and Grandio Flow, respectively. At the 24-month recall, the retention rate was 60% for Grandio and 54% for Grandio Flow. No statistically significant differences were found in retention rates among the restorative materials in any evaluation period (p > 0.05). For marginal discoloration and anatomical form, three Grandio and three Grandio Flow restorations showed Bravo scores at the end of 24 months. The restorations in both groups had Alfa ratings of 100% for the rest of the criteria evaluated. Conclusion: The nanohybrid and flowable resin composites showed similar clinical performances in the restoration of non-carious cervical lesions over 24 months. Keywords: nanohybrid composite, flowable composite, self-etching adhesive, cervical lesions, clinical trial