Objective: To compare effect of high-intensity (2200 mW/cm2) for 1 s with conventional intensity light-curing (1200 mW/cm2) for 20 s on clinical performance of bulk-fill resin composite restorations in compound class II cavities over 12 months follow-up. Material and methods: A total of 28 class II cavities were randomly restored with bulk-fill resin composite (n=14/group) and cured either with high-intensity (2200 mW/cm2) for 1 s (Intervention) or conventional intensity (1200 mW/cm2) for 20 s (Comparator). Modified USPHS criteria for marginal discoloration, marginal adaptation, secondary caries and postoperative sensitivity were used in the evaluation of restorations at baseline (1 week), 6 and 12 months. Results: There was no statistically significant difference between the two curing protocols at different follow-up intervals as regards the evaluated criteria (P > 0.05). High light intensity (2200 mW/cm2) for 1 s showed more risk (score B) when compared to conventional intensity (1200 mW/cm2) for 20 s, regarding marginal discoloration (RR = 5, P = 0.2851), marginal adaptation (RR = 2, P = 0.3737) and secondary caries (RR = 3, P = 0.4900), except for postoperative sensitivity with no risk for scores B and C (RR = 1, P = 1.0000). Conclusion: High-intensity light-curing (2200 mW/cm2) for 1 s has comparable clinical performance to conventional intensity light-curing (1200 mW/cm2) for 20 s for bulk-fill resin composite restorations in class II cavities.