Astragaloside IV (AsIV), one of the major active ingredients in Astragalus membranaceus, has demonstrated remarkable antifibrotic effects via its antioxidative activity. Cardiac fibrosis is an important pathological mechanism during cardiac remodelling associated with heart failure. In the present study, the mechanism underlying the antifibrotic effect of AsIV upon isoprenaline (ISO) stimulation was investigated. AsIV significantly improved cardiac fibrosis in vivo and dose‑dependently inhibited ISO‑induced CF proliferation in vitro. The ISO‑triggered elevation in reactive oxygen species (ROS) levels was remarkably inhibited by AsIV, as well as ROS scavenger N‑acetylcysteine (NAC), and not affected by cardiotrophin‑1 (CT‑1) knockdown. In addition, AsIV effectively reversed ISO‑induced upregulation of CT‑1 expression, which was blunted by pretreatment with NAC. Cardiac fibroblast (CF) proliferation and collagen Ι overexpression induced by ISO stimulation were effectively abrogated by AsIV, NAC, and CT‑1 small interfering RNA transfection. Taken together, these results demonstrated that AsIV was able to effectively inhibit ISO‑induced CF proliferation and collagen production through negative regulation of ROS‑mediated CT‑1 upregulation.