Objectives To compare guided bone regeneration (GBR) to connective tissue graft (CTG) in terms of increase in buccal soft tissue profile (BSP) at three-year follow-up when applied at the buccal aspect of single implant sites demonstrating a minor horizontal alveolar defect. Materials and methods Patients with a single tooth gap in the anterior maxilla and horizontal alveolar defect were enrolled in a single-blind RCT. All sites had a bucco-palatal bone dimension of at least 6 mm, received a single implant at least 3 months after tooth removal and were randomly allocated to the control (GBR) or test group (CTG) to re-establish buccal soft tissue convexity. Primary outcome was linear increase in BSP, meaning increase at the buccal aspect of the implant, based on superimposed digital surface models. Secondary outcomes were buccal bone and buccal soft tissue thickness, aesthetic and clinical parameters. Results Twenty-one patients were included per group at baseline. After three years, three patients in the GBR group and four in the CTG group were not willing to return for re-assessment. Hence, the final sample included 9 females/9 males (mean age 52) in the GBR group and 8 females / 9 males in the CTG group (mean age 49). The changes in BSP over time were not significantly different between GBR and CTG (p = 0.629). At three years, sites treated with GBR demonstrated 1.06 mm (95% CI: 0.83; 1.28) increase in BSP, whereas sites treated with CTG showed 0.99 mm (95% CI: 0.65; 1.35) increase in BSP (p = 0.699) compared to baseline. There were no significant differences between the groups for any of the parameters except for Mucosal Scarring Index, which was 1.63 (95% CI: 0.73; 2.53) lower for CTG (p = 0.002) at study termination. Conclusion There was no significant difference in linear increase in BSP between GBR and CTG after three years. Hence, clinical decision-making should be based on other factors.