IntroductionDespite tissue augmentation and management prior implantation, long‐term observation can reveal a change in peri‐implant phenotype with some lack of keratinized mucosa (KM). The treatment approach of peri‐implant dehiscence in multiple implants is not clearly defined. This report describes the different periodontal surgical approaches undertaken to promote the gingival margin stability and to prevent the peri‐implant mucosal inflammation over time.Case PresentationA 64‐year‐old woman with peri‐implant tissue dehiscence regarding implants placed 20 years ago in a calvarial bone grafted maxilla and mandible was treated. Right maxillary and mandible peri‐implants soft tissue were treated with a large apically positioned partial‐thickness flap (APPTF) combined to a free gingival graft (FGG) simultaneously. For the left maxillary, where a frenum was in tension associated with infection and pockets, a large APPTF followed by a FGG 4 months later were performed. The KM width (KMW) increased in three operated sites with a gain average of 2.2 mm. The plaque control record decreased from 68% to 21%. All the probing depths were lower than 3 mm. Bleeding on probing was significantly reduced. The gingival index (GI) went from 1.5 to 0.25.ConclusionIn a multiple implants soft tissue dehiscence case, an APPTF associate to a FGG, delayed or not, seems to be a safety primary approach to improve the KMW and to stabilize the peri‐implants soft tissue. Further, a connective tissue graft in a bilaminar approach could be an option to enhance soft tissue thickness and esthetic outcomes.Key pointsWhy is this case new information? To the best of the authors' knowledge, there are very limited studies regarding multi‐implant soft tissue dehiscence treatment. Relevant guidelines are not clearly defined. Despite peri‐implant hard and soft tissue augmentation, after a long‐term observation (20 years of function), we can observe a change in peri‐implant soft tissue phenotype (PISTP) with periodontal complication. What are the keys to successful management of this case? Removal of peri‐implant infection and tissue tension (frenum) by a large apically positioned partial‐thickness flap (APPTF) before soft tissue augmentation procedure. In case of very thin peri‐implant soft tissue, caution is needed to preserve the blood supply from the supra‐periosteal plexus. Large APPTF and sufficient amount of keratinized mucosa (KM) should be grafted to compensate for the tissue shrinkage. What are the primary limitations to success in this case? High esthetic demand. A secondary bilaminar approach with a connective tissue graft (CTG) should be necessary to improve the esthetic outcomes. Patient compliance.