Background: Peri-implant disease following successful integration of an endosseous implant is the result of an imbalance between bacterial load and host defense, which may affect not only the peri-implant mucosa but also involve the supporting bone. Objectives: The aim of this study was to evaluate the adjunctive effect of a dental water jet rinse mixed with chlorhexidine gel to the nonsurgical treatment for peri-implantitis. Method and Materials: A prospective randomized interventional cohort study was conducted. Forty consecutive patients presenting with peri-implantitis were recruited and randomly assigned into two treatment groups. Initially all patients received scaling/surface debridement and oral hygiene instruction. Patients in the study group received a water jet device containing chlorhexidine gel (Silonite®) for home use twice daily while the control group performed the recommended oral hygiene measures with no water jet usage. Three months following baseline visit, patients were reevaluated clinically and radiographically. Results: In total, 39 patients completed the study and were available for final examination. Three months following baseline visit the test group exhibited greater mean probing depth reduction (0.75 mm vs 0.27 mm; P = .029) as well as greater reduction in the number of sites presenting with bleeding on probing (2.26 vs 0.45 sites; P = .011). No significant change in bone level was observed at 3 months (mean bone gain was 0.18 mm). Conclusions: Water jet mixed with chlorhexidine gel might supplement the response to nonsurgical treatment for peri-implantitis lesions. Further, larger-cohort studies are warranted. Keywords: bone loss, disinfection, implant threads, peri-implant disease, peri-implant mucositis