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Aim: Senescence of alveolar type II (AT2) cells is an important driver of pulmonary fibrosis. This study aimed to investigate whether and how dysregulation of hydrogen sulfide (H2S) production affected AT2 cell senescence, and then explored the effect of H2S on the communication between AT2 and fibroblasts. Methods: ICR mice were intratracheally administered with bleomycin (3 mg/kg). Sodium hydrosulfide (NaHS, 28 μmol/kg/d) was intraperitoneally injected for 2 weeks. The H2S‐generating enzyme cystathionine‐β‐synthase (CBS) knockout heterozygous (CBS+/−) mice were used as a low H2S production model. Results: Analysis of microarray datasets revealed downregulation of H2S‐generating enzymes in lung tissues of patients with pulmonary fibrosis. Decreased H2S production was correlated with higher levels of cell senescence markers p53 and p21 in bleomycin‐induced lung fibrosis. CBS+/− mice exhibited increased levels of p53 and p21. The numbers of AT2 cells positive for p53 and p21 were increased in CBS+/− mice as compared to control mice. H2S donor NaHS attenuated bleomycin‐induced AT2 cell senescence both in vivo and in vitro. H2S donor suppressed bleomycin‐induced senescence‐associated secretory phenotype (SASP) of AT2 cells via inhibiting p53/p21 pathway, consequently suppressing proliferation and myofibroblast transdifferentiation of fibroblasts. Mechanically, H2S suppressed p53 expression by enhancing the mouse double‐minute 2 homologue (MDM2)‐mediated ubiquitination and degradation of p53. Conclusion: H2S inactivated p53‐p21 pathway, consequently suppressing AT2 cell senescence as well as cell communication between senescent AT2 cells and fibroblasts. Aberrant H2S synthesis may contribute to the development of pulmonary fibrosis through promoting the activation loop involving senescent AT2 cells and activated fibroblasts. [ABSTRACT FROM AUTHOR]