Three patients diagnosed with peri-implant disease after osseointegration exhibited soft tissue oedema and fistulae. Treatment options for controlling the fistulae were investigated. Free subepithelial connective tissue grafts (SCTGs) and microinvasive surgery were used to improve the soft tissue biotype of the patients with fistulae. After SCTG surgery, the fistulae disappeared. The clinical outcomes were stable and aesthetic outcomes were satisfactory after 3–5 years of follow-up. Based on this study, utilising SCTG to improve the tissue biotype may be an effective clinical approach for controlling fistulae occurring during peri-implant disease. Keywords: connective tissue, follow-up, microinvasive surgery, peri-implant disease, tissue biotype