Patients with diabetes present a worse response to periodontal treatment. Local antimicrobials as an adjunct to scaling and root planing (SRP) provide additional benefits in the treatment of periodontitis in healthy patients. This review aims to evaluate the effects of local antimicrobials as an adjunct to SRP, compared with SRP alone, on periodontal clinical parameters of patients with chronic periodontitis (CP) and diabetes mellitus (DM). Only randomized controlled trials with: 1) at least 6 months of follow-up; 2) SRP, in combination with local antimicrobials; and 3) patients with periodontitis and DM were considered eligible. MEDLINE, EMBASE, and LILACS databases were searched for articles published up to January 2016. Random-effects meta-analyses were conducted for clinical attachment level (CAL), probing depth (PD), bleeding on probing, and gingival index change after treatment. Of 153 papers potentially relevant to this review, six were included. The majority of trials showed a significant PD reduction and CAL gain associated with use of local antimicrobials in patients with type 1 and type 2 DM. Only studies that included well-controlled patients and applied antimicrobials at the deepest sites or sites with baseline PD ≥5 mm presented significant PD reduction and CAL gain. In patients with DM and CP, use of local antimicrobials as an adjunct to SRP may result in additional benefits compared with SRP alone in PD reduction and CAL gain, especially in well-controlled individuals and deep sites.