AbstractBackgroundβ‐asarone (β‐as), a compound extracted from Acorus calamus, has been found to have anticancer effects on a variety of human cancers. However, the potential effect of β‐as on bladder cancer (BCa) remains unknown.MethodsAfter exposure to β‐as, migration, invasion, and epithelial‐mesenchymal transition (EMT) of BCa were determined by wound healing, transwell, and Western blot assays. Expression of proteins involved in the EMT and ER stress were explored by Western blot assays. Nude mouse xenograft model was served as the model system in vivo.ResultsThe migration, invasion, and EMT of BCa were significantly inhibited after β‐as treatment. Further experiments revealed that endoplasmic reticulum (ER) stress is involved in β‐as‐mediated metastasis inhibition. In addition, β‐as significantly up‐regulated activating transcription factor 6 (ATF6), a branch of ER stress, and promoted its Golgi cleavage and nuclear localization. ATF6 silencing attenuated β‐as‐mediated metastasis and EMT inhibition in BCa cells.ConclusionOur data suggests that β‐as inhibits migration, invasion, and EMT of BCa by activating the ATF6 branch of ER stress. Thus, β‐as represents a potential candidate for BCa treatment.