Purpose: To evaluate the clinical efficacy of the coronally advanced lingual flap (CALF) technique in terms of the extent of lingual and buccal flap advancement, the maintenance of primary wound closure, and safety in comparison to buccal flap advancement alone during horizontal ridge augmentation in the posterior mandible. Materials and Methods: A total of 14 patients were randomly allocated to two different groups: buccal flap advancement without the CALF technique (control), referred to as the NO-CALF group, and buccal flap advancement with the CALF technique (test), referred to as the CALF group. Wound healing was monitored weekly for the first 4 weeks, then at 2, 4, 6, and 9 months postoperatively for any soft tissue dehiscence (titanium mesh [TM] exposure) along the incision line. The extent of lingual and buccal flap advancement was measured, and any intraoperative and postoperative CALF-related complications were reported. Results: The difference between groups was statistically significant (P < .0001) in terms of (1) TM exposure: 83.3% of cases in the NO-CALF group showed early Class П exposures, whereas the CALF group showed no exposure; (2) mean lingual flap advancement: 3.9 ± 1.1 mm and 14.4 ± 3.8 mm for the NO-CALF and CALF groups, respectively; and (3) mean buccal flap advancement: 15.8 ± 2.1 mm and 10.5 ± 1.4 mm for the NO-CALF and CALF groups, respectively. There were no reported complications related to the CALF technique. Conclusion: Tension-free primary wound closure was facilitated and maintained during the healing period by applying the CALF technique, which is a reliable technique to safely advance the lingual flap coronally.