The objective of this study was to analyze and assess the clinical performance of direct composite restorations using a nanohybrid and a nanofill composite material for posterior teeth in patients with amelogenesis imperfecta (AI). This study involved 15 patients between the ages of 14 and 30 years suffering from amelogenesis imperfecta (AI). During the study, the patients received direct composite restorations using either the Clearfil Majesty ES-2 (Kuraray Medical Inc, Tokyo, Japan) and Clearfil Universal Bond (Kuraray) or Filtek Ultimate Universal Restorative (3M ESPE, St Paul, MN, USA) and Single Bond Universal Adhesive (3M ESPE). The evaluations of the restorations were conducted per the modified USPHS criteria at the time of baseline as well as during the first-, second-, third-, and fourth-year follow-up sessions. After four years, it was observed that the cumulative success rate of direct posterior restorations was 98.1% for Clearfil Majesty ES-2 and 92.2% for Filtek Ultimate. During the study one Clearfil Majesty ES-2 restoration and four Filtek Ultimate restorations failed. There was a significant difference between Clearfil Majesty ES-2 and Filtek Ultimate in the color match in posterior restorations after three and four years. The causes of failure included marginal discoloration and caries, as well as fracture of the restoration. Hence, it can be stated that the use of nanohybrid or nanofill composites in posterior direct restorations in patients with AI looks promising. The failure rate of Clearfil Majesty ES-2 was found to be lower than that of Filtek Ultimate restorations. Clinically, the rate of optimum restorations conducted for partial discoloration, marginal adaptation, color match, and surface texture were observed to be higher when Clearfil Majesty ES-2 was used. However, additional studies are needed to assess the clinical performance of direct posterior composite materials in patients with AI.