OBJECTIVE: This prospective clinical study aimed to evaluate the two-year clinical performance of conventional composite, bulk-fill composite, and high-filler flowable composite in Class II cavities. MATERIALS AND METHODS: A total of 259 Class II restorations were performed in 110 patients, applying Clearfil Majesty Posterior (Clearfil) as the conventional composite, Filtek One Bulk Fill Restorative (Filtek) as the bulk-fill composite, and G-aenial Universal Injectable (G-aenial) as the high-fill flowable composite. G-Premio Bond, a universal adhesive system, was applied for all composite resin restorations. Restorations were evaluated using FDI criteria after 2 years. Data were analyzed using the Kruskal-Wallis and Friedman tests. RESULTS: At the end of two years, the group treated with Clearfil has showed a significantly higher surface gloss score compared to the G-aenial and Filtek groups. Additionally, it was seen that the marginal adaptation scores of the Clearfil group were similar to the Filtek group and significantly higher than the G-aenial group. In intra-group evaluations, the contact point scores of the Clearfil group showed a statistically significant increase compared to baseline and one-year follow-up assessments. The marginal adaptation scores of the Clearfil and Filtek groups also exhibited a statistically significant increase compared to baseline and one-year follow-up assessments. CONCLUSIONS: High-filler flowable composite and bulk-fill composite exhibited better clinical properties regarding surface gloss compared to conventional composite. It was observed that the marginal adaptation property of the conventional composite were similar to the bulk-fill composite and lower than the high- filler flowable composite. CLINICAL RELEVANCE: The composite resins tested showed similar results in most of the scores evaluated.