Aims: This aim of this study is to evaluate and to compare the clinical performances of two nanohybrid composite resin systems used for diastema closure and tooth reshaping at 4 years. Subjects and Methods: Twenty-three patients with midline or multidiastema problem were enrolled in this study. Nanohybrid resin composite systems to be used on each patient were randomly selected. Thirty seven teeth of 10 patients were restored with Filtek-Z550 (3M/ESPE) in combination with Adper (TM) Single Bond 2 (3M/ESPE) etch and rinse adhesive in Group 1 whereas 39 teeth of 13 patients were restored with Charisma-Diamond (Heraeus Kulzer) in combination with Gluma2 Bond (Heraeus Kulzer) etch and rinse adhesive in Group 2, by two operators. Esthetic, functional, and biological properties of the restorations were evaluated at baseline, 1, 2, 3, and 4 years using foreign direct investment criteria by two independent examiners. Statistical Analysis Used: The data were evaluated using Fisher's Chi-Square (P = 0.05). Results: Fifty-eight restorations (19 patients) with a mean service time of 43.4 months were evaluated (recall rate 82.6%). One Filtek-Z550 and two Charisma-Diamond restorations were repaired due to partial fracture (Score 4). Survival rates of Group 1 and Group 2 were 96.3% and 93.5%, respectively (Kaplan-Meier) (P > 0.05). Qualitative deteriorations were observed within each group according to baseline regarding surface luster, surface/marginal staining, marginal adaptation, patient's view, and periodontal response (P < 0.05). However, there were no significant differences between two restorative materials for any of the criteria assessed (P > 0.05). Conclusions: Both nanohybrid composite resin systems revealed esthetically, functionally, and biologically acceptable clinical performance when used for diastema closure and tooth reshaping at 4 years.