Introduction: This study investigated the effects of keratinized mucosa width (KMW) on peri-implant tissues by evaluating peri-implant clinical and bone resorption parameters. Subjects and Methods: Seventy-one dental implants (DIs) were separated based on adequacy/inadequacy of KMW. DIs with inadequacy KMW were grouped as peri-implant plastic surgery (PIPS) (free gingival graft/free periosteal graft groups) and maintenance (M) groups. DIs with adequacy KMW were grouped as the controls. Peri-implant clinical parameters were measured at the baseline and 6(th) month. Levels of receptor activator of nuclear factor B ligand (RANKL) and osteoprotegerin (OPG) in peri-implant sulcular fluid were determined after clinical measurements using enzyme-linked immunosorbent assay. Results: In baseline, gingival index, bleeding on probing, and plaque index (PI) were lower in controls compared to the PIPS and M groups, and KMW was higher. At 6(th) month, peri-implant pocket depth and PI were lower in the PIPS groups and controls compared to the M group, and KMW was higher. While RANKL and OPG values and RANKL/OPG ratio at baseline were not significantly different between groups, OPG concentration and RANKL/OPG ratio in the 6(th) month were higher in the PIPS group compared to the M group (P < 0.05). The RANKL/OPG ratio decreased at 6(th) month in the PIPS groups and controls (P < 0.05). Positive and negative correlations were observed between peri-implant clinical and osteoimmunological parameters. Conclusion: This study demonstrated that adequate KMW and PIPS techniques exhibited positive effects on clinical peri-implant parameters and osteoimmunological mediators.