Epithelial-mesenchymal transition (EMT) induced by transforming growth factor-β (TGF-β) is involved in hepatocellular carcinoma (HCC) growth and metastasis. Our study aimed to investigate the role of molecules interacting with CasL 1 (MICAL1) in regulating TGF-β-triggered EMT in HCC and the related mechanisms. After detecting MICAL1 expression and prognostic value in HCC, in vitro assays including CCK-8 assay, EdU staining, flow cytometry assay, Transwell assay, western blotting, and RT-qPCR and in vivo metastasis assay was conducted to evaluate the influence of MICAL1 knockdown on the proliferation and apoptosis as well as TGF-β-induced EMT and metastasis of Huh7 and MHCC97H cells. MICAL1 was highly expressed in HCC, and its high expression was related to histological grade, TNM stage, and shorter overall survival of HCC patients. MICAL1 silencing suppressed proliferation, promoted apoptosis, and curbed TGF-β1-triggered cytoskeletal remodeling, EMT, and metastasis of HCC cells. MICAL1 knockdown impeded TGF-β1-induced upregulation in phosphorylated-Smad2/3 protein levels and reduced Smad2/3 mRNA levels in HCC cells. MICAL1 downregulation enhanced the polyubiquitination and proteasomal degradation of TβRI. Additionally, MICAL1 silencing suppressed tumor growth and lung metastasis in Huh7-derived xenograft mouse models. Collectively, MICAL1 knockdown impairs TGF-β1-stimulated EMT and metastasis of HCC cells by restraining Smad2/3 phosphorylation and activation.