Mucogingival deformities around implants are frequent findings in clinical practice and often present as inadequate keratinized tissue and insufficient mucosal thickness. Phenotype modification therapy can increase peri-implant mucosal thickness and the amount of keratinized mucosa, improving the long-term clinical outcomes of implants. Free gingival graft (FGG) is considered the gold standard to increase keratinized mucosa; however, FGGs on lingual aspects of implants are less predictable due to technique sensitivity and often present with insufficient gain in tissue thickness ue to limited blood supply. The Semilunar Lingualized Apically Positioned Flap (SLAP) with subperiosteal tunnel connective tissue graft (CTG) can increase both peri-implant mucosal thickness and keratinized mucosal width circumferentially. SLAP consists of one full-thickness, semilunar incision within keratinized mucosa on the buccal, and two vertical releasing incisions mesial and distal of the implant, extending lingually into the alveolar mucosa. The tissue is apically positioned lingual to the implant, and sutured in place creating buccal space for CTG via buccal subperiosteal tunneling. SLAP is a minimally invasive and predictable approach in improving peri-implant mucosal phenotype. This case reports demonstrates gain in peri-implant mucosal thickness and the amount of keratinized mucosa over a 10-month period utilizing SLAP with subepithelial CTG.