Background: Cytokine-producing B cells play a well-established role in modifying immune responses in chronic inflammatory diseases. We characterized B-cell cytokine responses against periodontitis-associated bacteria in patients with periodontitis. Methods: Blood and saliva samples were collected from patients with periodontitis grade B (N = 31) or grade C (N = 25), and 25 healthy controls (HCs). Mononuclear cells were stimulated with Porphyromonas gingivalis, Fusobacterium nucleatum, Staphylococcus epidermidis, or Cutibacterium acnes, and B-cell production of tumor necrosis factor (TNF)-α, interleukin (IL)-6, interferon (IFN)-γ, IL-10 and transforming growth factor (TGF)-β by B cells was assessed by flow cytometry. Results: HCs had higher baseline frequencies of B cells producing IFN-γ or TNF-α than grade B patients, but only B cells from grade B patients showed significant differentiation into IFN-γ-, TNF-α-, TGF-β-, or IL-10-producing cells after challenge with P. gingivalis and into IFN-γ-, TGF-β-, or IL-10-producing cells after challenge F. nucleatum. Notably, the baseline frequency of IL-10-producing B cells from grade C patients correlated inversely with clinical attachment loss (AL). The major proportion of the IFN-γ- and TGF-β-producing B cells were CD27⁺ memory cells, while the IL-10‒producing B cells were mainly CD27⁻CD5⁻. Conclusions: B cells from grade B patients, particularly those harboring P. gingivalis, showed proinflammatory B-cell responses to P. gingivalis. Moreover, the baseline frequency of IL-10-producing B cells in the grade C group correlated inversely with AL, suggesting a diminished immunoregulatory capacity of IL-10‒producing B cells in these patients.