The effect of probiotic milk drinks associated with non-surgical periodontal therapy (NSPT) in treating periodontitis was evaluated. A double-blind placebo-controlled randomized clinical trial with patients with periodontitis was conducted. Two groups were used: TG (n=15, test group, probiotic milk drink, Lacticaseibacillus casei 01, 8-9 log CFU/mL) and CG (n=15, control group, conventional milk drink). The milk drinks (100 mL) were consumed once a day at breakfast for 15 days. Both groups also received NSPT, supra and subgingival scaling and root planning per quadrant, and oral hygiene instruction. All patients were clinically evaluated after 30, 90, and 180 days of the last NSPT session. Reductions in clinical attachment loss and probing pocket depth were observed at 30 days in both groups, maintained throughout the follow-up. Decreases in visible plaque index (VPI) and bleeding on probing were observed after probiotic milk drink consumption for 30 days, suggesting an effect provided by probiotics in the control of biofilm and inflammation. However, the impact on VPI was not persistent for more than 30 days, demonstrating the need for regular consumption of the probiotic milk drink. In conclusion, probiotic milk drinks may be used as adjuvant therapy to treat periodontitis.