Aim: This randomized placebo‐controlled clinical trial evaluated the effect of Bifidobacterium animalis subsp. lactis (B. lactis) HN019‐containing probiotic lozenges as adjuvant to scaling and root planing (SRP) in patients with generalized chronic periodontitis.Materials and Methods: Forty‐one chronic periodontitis patients were recruited and monitored clinically, immunologically, and microbiologically at baseline (before SRP) and 30 and 90 days after SRP. All patients were randomly assigned to a Test (SRP + Probiotic, n = 20) or Control (SRP + Placebo, n = 21) group. The probiotic lozenges were used twice a day for 30 days. The data were statistically analysed.Results: The Test group presented a decrease in probing pocket depth and a clinical attachment gain significantly higher than those of the Control group at 90 days. The Test group also demonstrated significantly fewer periodontal pathogens of red and orange complexes, as well as lower proinflammatory cytokine levels when compared to the Control group. Only the Test group showed an increase in the number of B. lactis HN019 DNA copies on subgingival biofilm at 30 and 90 days.Conclusion: The use of B. lactis HN019 as an adjunct to SRP promotes additional clinical, microbiological, and immunological benefits in the treatment of chronic periodontitis (NCT03408548).