Purpose: The aim of this systematic review was to investigate the effect of keratinized mucosa width (KMW) on clinical parameters of peri-implant health and stability. Materials and Methods: Two independent reviewers conducted a comprehensive search to identify studies on human subjects reporting KMW as a bivariate factor (≥ 2 mm and 2 mm), along with mean pocket depth (PD), bleeding on probing (BOP), modified Bleeding Index (mBI), Gingival Index (GI), Plaque Index (PI), modified PI (mPI), and implant survival with a minimum follow-up of 6 months after implant loading. Eight studies were included in the systematic review and seven in the metaanalyses to ascertain summary effects for differences in the aforementioned parameters among groups of KMW. Results: Pooled analyses showed that GI, PI, and mPI were significantly higher in the group with KMW of 2 mm, while mBI was also higher but only marginally significant. In contrast, PD was not significantly different between the two groups. Differences in BOP and implant survival rate could not be analyzed because of limited data availability. Heterogeneity was highly significant among the pooled studies for all investigated variables. Conclusion: Reduced KMW around implants appears to be associated with clinical parameters indicative of inflammation and poor oral hygiene. However, based on the selected evidence, the predictive value of KMW is limited.