Objectives: This study aimed to evaluate the 1-year clinical performance of Ribbond-reinforced direct composite restorations placed in different orientations in endodontically treated posterior teeth.Materials and Methods: This clinical observational study was approved by the Selçuk University Faculty of Dentistry Ethics Committee (Approval No: 2023/54). Eighty-five patients (59 females, 26 males; aged 18–50 years) with 90 endodontically treated posterior teeth were included. Restorations were performed using a two-step self-etch adhesive (Clearfil SE Bond), a highly filled injectable composite (G-aenial Universal Injectable), a nanohybrid composite (G-aenial A’CHORD), and polyethylene fiber (Ribbond). Based on cavity configuration, fibers were placed in three orientations: circumferential (O-shaped), mesiodistal (MD), and buccolingual (BL). Clinical performance was assessed using modified USPHS criteria at 1 week, 6 months, and 12 months. Statistical analyses were performed using R software (v4.1.2) (p < 0.05).Results: All restorations demonstrated high clinical success, with no significant time-dependent deterioration. No statistically significant differences were observed among fiber orientation groups for any evaluated parameter (p > 0.05).Conclusions: Ribbond-reinforced composite restorations showed consistently favorable clinical performance over 12 months. Fiber orientation did not significantly influence outcomes, suggesting that clinically simplified placement strategies may be sufficient in the restoration of endodontically treated posterior teeth.