OBJECTIVES: Transmembrane serine protease 2 (TMPRSS2) plays a key role in the entry of viruses such as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and influenza A into host cells, and its elevated expression is a risk factor for the spread of viral infection. However, TMPRSS2 expression and the factors related to its induction in oral keratinocytes and fibroblasts remain largely unknown. Here, we examined TMPRSS2 expression and factors related to its induction in oral mucosal cells. METHODS: TMPRSS2 expression was examined in oral keratinocytes (RT7) and fibroblasts (GT1). Subsequently, TMPRSS2 induction in was analyzed in both cell types following transfection of nucleic acid and inflammatory cytokines, such as interleukin (IL)-1β. Finally, the effects of IL-1β on STAT1 activation related to double-stranded RNA (dsRNA)-induced TMPRSS2 expression were examined. RESULTS: RT7 and GT1 cells exhibited constitutive TMPRSS2 mRNA and protein expression. Transfection with Poly(I:C) (as a dsRNA) and poly (dA:dT) (as a double-stranded DNA [dsDNA]) increased TMPRSS2 expression. TMPRSS2 expression was also increased by IL-1β, but not IFN-γ or TNF-α, while the combination of IL-1β and transfected Poly(I:C) caused a dramatic increase in TMPRSS2 expression as compared to each alone in both cell types. IL-1β also enhanced transfected Poly(I:C)-activated STAT1 related to TMPRSS2 expression. CONCLUSIONS: TMPRSS2-expressing oral keratinocytes and fibroblasts are targets of SARS-CoV-2 and influenza A virus. TMPRSS2 expression, in cooperation with IL-1β, plays an important role in promoting infection during virus invasion in oral mucosal cells.