Interleukin‐24 is a pleiotropic immunoregulatory cytokine and a member of the IL‐20R subfamily of the IL‐10 family. The aim of this study was to investigate the regulation of IL‐24 in the human oral keratinocyte cell line HOK‐16B following infection with Tannerella forsythia, a major periodontal pathogen. T. forsythia induced the expression of IL‐24 mRNA and the secretion of glycosylated IL‐24 in HOK‐16B cells. Glycosylation of IL‐24 is linked to its solubility and bioavailability. T. forsythia‐stimulated reactive oxygen species (ROS) induced the expression of IL‐24, which was regulated by IL‐6. The ROS inhibitor N‐acetylcysteine and MAPK inhibitors significantly reduced the expression of IL‐6 and IL‐24 induced by T. forsythia. Recombinant human IL‐24 significantly enhanced the expression of IL‐1α, IL‐8, CXCL10, and MCP‐1 in HOK‐16B cells. Together, these results indicate that ROS, MAPKs, and IL‐6 comprise the axis of IL‐24 expression in HOK‐16B cells stimulated with T. forsythia. Thus, IL‐24 may be involved in inflammation in oral keratinocytes.