Diabetes mellitus (DM) is a widely prevalent disease associated with several major systemic and oral complications, such as periodontitis. The use of adjunctive local and/or systemic antimicrobials has been proposed to improve the clinical and glycemic outcomes of the scaling and root planing (SRP) in diabetic subjects. The combination of metronidazole (MTZ) and amoxicillin (AMX) has been largely recognized as an effective therapy for improving the clinical and microbiological outcomes of SRP in the treatment of with chronic periodontitis (ChP). However, no previous clinical trials to date have evaluated the effects of this antibiotic combination in the treatment of diabetic subjects with periodontitis. Therefore, the aim of this randomized clinical trial (RCT) will be to evaluate the clinical and microbiological effects of the use of MTZ+AMX as adjuncts to SRP for the treatment of type 2 diabetic subjects with generalized ChP.