B Background: Nanohybrid composite resin is a type of composite consisting 2different filler sizes, where one of the filler size ranges in nanoparticles around 0.01-0.05μm. Pineapple juice (Ananas comosus) is a widely consumed drink byIndonesian with pH range 3.5-4.6. Surface roughness may be affected by extrinsicfactors such as low pH from pineapple juice. Rough surface can cause bacterialadhesion and plaque accumulation on restorative material which cause secondarycaries, gingivitis and staining. Preheating is a preparation method of compositewhich improve composite physical and mechanical properties. Objective: Thisstudy aimed to determine the impact of immersion in pineapple juice to the surfaceroughness of preheated and non-preheated composite resin. Method: This researchwas a laboratory experimental using post-test with control group design to 36samples divided into 3 groups namely preheated, non-preheated and control.Preheated and non-preheated groups will be immersed in 10 mL pineapple juice pH3.5-4.6 2 hour every day for 12 days with cycling method, while control groupimmersed in distilled water. Then surface roughness is measured with surfaceroughness tester and analysed using one way ANOVA followed by Post Hoc Tukey.Result: One-way analysis of variance (ANOVA) showed significant result of p =0.034. Post hoc Tukey’s analysis revealed p = 0.03 showing significant differencein surface roughness of non-preheated composite resin with control group, but nosignificant differences was found between preheated and non-preheated groups.Conclusion: Immersion of non-preheated nanohybrid composite resin in pineapplejuice for 2 hour for 12 days shows significant increase in its surface roughness .