Objectives The gingival thickness (GT) and keratinized tissue (KT) height are defined as the gingival phenotype. Both the modified coronally advanced tunnel technique (MCAT) and free gingival grafts (FGG) are used in modifying the gingival phenotype. This study aims to compare MCAT and FGG in gingival phenotype modification. Materials and methods One hundred and forty recessions in 50 patients with thin and insufficient keratinized tissue at the anterior mandible were treated with either MCAT or FGG. GT, KT height, recession depth, recession width, probing depth, and clinical attachment level were evaluated at baseline and 6 weeks, 6 months, and 12 months. GT change, KT change, root coverage (RC), clinical attachment gain, and complete root coverage (CRC) were calculated. The wound healing index, tissue appearance, patient expectations, aesthetic, and dentin hypersensitivity were assessed at baseline and 6 months. Results All periodontal variables showed significant change from baseline to 12 months in both groups (p < 0.05). While FGG resulted in more KT change (p < 0.001), all MCAT sites showed at least 2 mm KT change in 12 months. MCAT resulted in greater GT change (p < 0.05) and RC (p < 0.003). In contrast, there was no significant inter-group CRC difference (p = 0.523). All patient-based variables were favorable to MCAT (p < 0.05), except dentin hypersensitivity (p = 0.225). Conclusions Both techniques were successful in terms of gingival phenotype modification in the anterior mandible. Additional GT increase, RC, and patient-based outcomes favored MCAT, though KT change proved greater with FGG.