Background: The effect of keratinized mucosa on peri-implant tissue health is still inconclusive. This study aimed to evaluate the importance of keratinized mucosa and investigate the impact of the free gingival graft procedure on peri-implant health. Methods: At prosthesis delivery, the implants were allocated into three groups, based on the width of keratinized mucosa (KM) and patients' agreement on the free gingival graft procedure: KMS (KM ≥2 mm), KMD (KM <2 mm), and FGG (KM <2 mm initially and having surgically increased keratinized mucosa). Modified plaque index (mPI), probing depth (PD), modified bleeding index (mBI), KM, and marginal bone loss (MBL) were assessed at the baseline, 6-, 12-, and 24-month follow-up periods. Results: Of the 47 patients, 17 belonged to the KMS group, 17 belonged to the KMD, and the remaining 13 patients belonged to the FGG. KMD demonstrated significantly fewer mPI and higher mBI than KMS and FGG at 6 and 12 months. At 24 months, MBL did not differ between the groups; however, PD was significantly greater in the KMD group. Conclusions: Implants with inadequate keratinized mucosa had higher bleeding and pocket depth values despite less plaque accumulation. According to the results, soft tissue grafting should be performed as early as possible. © 2023 Australian Dental Association.