ObjectiveRho GTPase-activating protein 30 (ARHGAP30), a member of the Rho GTPase-activating proteins (Rho GAPs) family, plays an important role in the regulation of cytoskeleton organization and cell adhesion.Materials and methodsmRNA and protein expression was assessed by quantitative real-time PCR and Western blotting, respectively. Cell Counting Kit-8 (CCK-8) and Transwell assays were conducted to detect cell proliferation, migration, and invasion.ResultsARHGAP30 expression was downregulated in specimens and cell lines of lung cancer in comparison to non-cancerous specimens and normal bronchial epithelial cell lines, respectively. Moreover, in vitro experiments demonstrated that ARHGAP30 overexpression impeded the proliferative, migratory, and invasive abilities of lung cancer cells. Moreover, bioinformatics analysis with The Cancer Genome Atlas (TCGA) lung cancer dataset showed a negative association between ARHGAP30 expression and the Wnt signaling pathway. Enforced expression of ARHGAP30 decreased the mRNA and protein levels of β-catenin, c-Myc, matrix metalloproteinase-2 (MMP-2) and MMP-9. Besides, the β-catenin inhibitor XAV939 blocked the enhanced cell growth, migration, and invasion caused by ARHGAP30 knockdown. Thus, the Wnt/β-catenin pathway mediated the functions of ARHGAP30 in lung cancer cells.ConclusionARHGAP30 acts as a tumor suppressor in lung cancer by suppressing Wnt/β-catenin signaling.