Diabetic patients are more prone to develop infections such as periodontal diseases. Bacteriotherapy with the concept of using good bacterial strains to replace the pathogenic ones emerged as a fascinating field due to the increasing incidence of antibiotic resistance. The aim of this study was to evaluate if a particular combination of probiotics (Lactobacillus Reuteri DSM 17938 and Lactobaciullus Reuteri ATCC PTA 5289) is useful in treating gingivitis in diabetic patients. Eighty adult patients with diagnosis of controlled diabetes type II and gingivitis were enrolled for this study and randomized in two groups. Only oral hygiene instructions were given. Bacteriotherapy (Lactobacillus Reuteri) was administered to test group. Outcome measures were presence of Plaque (P.I.) and Bleeding on Probing (B.O.P.). Data were collected at baseline and after 30 days. At 30 days, both groups showed a statistically significant clinical indexes reduction from baseline. More reduction was present in the test group for P.I. (14%±6) and for B.O.P. (18%±4) and was statistically significant (p less than 0.05). Within the limitations of this study, bacteriotherapy can be considered effective in reducing plaque and BOP in patients with controlled diabetes type II and gingivitis.