Objectives To assess changes in gingival thickness (GTH) and the width of keratinized gingival tissue (KTW) following treatment with either connective tissue graft (CTG) or an albumin gel-platelet-rich fibrin mixture (Alb-PRF). Materials and methods Twenty treatment sites were included in a split-mouth design involving 10 patients with a thin gingival phenotype in the mandibular anterior region. The sample was randomly divided into two groups, with the Alb-PRF applied to the experimental group and CTG used for the control group. GTH and KTW were measured at baseline and after one, three, and six months. Results GTH increased in both groups during all follow-up periods. However, no statistically significant differences (p > 0.05) between the groups were observed at baseline and six months. At three months, the experimental group exhibited significantly higher GTH (p < 0.001). Additionally, at three and six months, the CTG group showed a superior increase in KTW (p < 0.05). Conclusion Within the constraints of this study, Alb-PRF application for modifying thin gingival phenotypes proved to be an effective therapeutic option, potentially serving as an alternative to CTGs. Although Alb-PRF resulted in thicker gingiva, CTG demonstrated a greater enhancement in KTW.