Objectives: This clinical study aimed to compare the free gingival graft from the palate (FGG) with a new porcine collagen matrix (CM, Mucograft) in terms of augmenting the keratinized peri-implant mucosa, based on clinical and histological assessments. Methods: The study included 14 patients that underwent a vestibuloplasty, either with a FGG from the palate (n=7) or with the CM (n=7). An implant-fixed vestibular retention splint was inserted for 30 days. Follow-up examinations were performed at 4, 10, 30, and 90 days post-surgery. Width of keratinized mucosa was measured in the region of each implant (10th, 30th and 90th day). After 90 days, a biopsy was harvested for histological and immunohistological analyses. To characterize newly formed soft tissue, we stained for tissue and differentiation-specific markers, cytokeratin (CK) 5/6, 13, and 14, to detect presence or absence of keratinization. Results: The groups showed similar healing, with increased peri-implant keratinized mucosa. The CM group had overall significantly shorter operation times than the FGG group. Both groups showed similar overall shrinkage (CM 32.98% vs. FGG 28.35%) after 90 days. All biopsies showed a multilayered, keratinized, squamous epithelium. Cytokeratins 5/6 and 14 were detected in the basal and suprabasal layers, and spots of cytokeratin 13 were detected in the suprabasal layers. CK expressions were similar to cytokeratin expression patters of keratinized gingiva. Conclusions: During the whole observation period, both groups showed comparable clinical and histologic outcomes. Within the limitations of the present study, CM seems to be a promising alternative for the regeneration of keratinized mucosa without tissue harvesting. Comparative long-term studies are needed to investigate changes over time. Keywords: dental implants, collagen, transplants, clinical trial, dental materials, keratins