Introduction: The formation of bacterial biofilms by opportunistic microorganisms on the surfaces of the implants is the leading etiopathogenetic factor of peri-implant mucositis and peri-implantitis. The purpose of this research was to study the adhesive and biofilm-forming properties of clinical strains of K. kristinae isolated from patients with peri-implant mucositis. Methods: 18 clinical strains of K. kristinae isolated from the patients were the object of the study. The adhesion of the microorganisms was determined by using formalized human red blood cells of the blood group O (1) Rh+ by the G. Brilis technique. The study of biofilm-forming properties of clinical isolates of K. kristinae was performed by using the spectrophotometric technique by G.D. Christensen (MtP microtiter plate test). Results: The representatives of genus Kocuria were isolated in 70% of patients. Total proportion of clinical isolates of Kocuria spp. among all isolated microorganisms reached 18.3%. The representatives of the species K. kristinae showed a high adhesion to red blood cells and high ability to form biofilms. The r-Pearson coefficient (+0.87) between adhesion and the ability to form biofilms by K. kristinae strains pointed out a direct correlation. Conclusions: Obviously, Kocuria spp. take part in peri-implant mucositis development. It is proved by their presence on the mucous membrane of peri-implant area of patients with complications after dental implant placement. The representatives of the species K. kristinae showed a high adhesion and high biofilmformation.