Background: Dental caries is a chronic dental disease due to microbial metabolic activity, which causes tooth demineralization. Dental caries prevalence in Indonesia in 2018 was 45.3%. The prevalence value of dental caries can be reduced by restoring teeth and maintaining oral hygiene. One of the dental restoration materials is nanohybrid composite resin. Basil leaf extract solution (Ocimum sanctum) has the potential to be used as a mouthwash because it contains eugenol and polyphenols, which have antibacterial properties against Streptococcus mutans at concentrations of 2% and 4% to improve oral hygiene and prevent primary and secondary caries. Secondary caries occurs due to bacteria's attachment and penetration of restorative materials with a rough surface. The surface roughness of the composite increased after exposure to eugenol and polyphenols. Purpose: To determine the effect of exposure to a solution of Ocimum sanctum leaf extract concentration of 2% and 4% on the surface roughness of nanohybrid composite resin. Methods: Plant determination, phytochemical test, acidity test, immersion for five days, and surface roughness test. Results: Ocimum sanctum leaf extract contains 0.21% eugenol and 5.11% polyphenols, and the extract solution has a pH of 4.7. The mean increase in surface roughness on the top and bottom surfaces of the nanohybrid composites after exposure to 2% and 4% Ocimum sanctum leaf extract solutions was significantly different from exposure to distilled water (p<0.05). Conclusion: Exposure to Ocimum sanctum leaf extract solution increased the surface roughness of nanohybrid composite resin.