Sarcopenia is characterized by age-related muscle mass/function loss and fibrosis. Satellite cell (SC) dysfunction during aging promotes fibrotic transdifferentiation and extracellular matrix (ECM) deposition. Cyr61, a pro-fibrotic matricellular protein, and Wnt/β-catenin signaling pathway are implicated in muscle regeneration-fibrosis balance, but their interaction in sarcopenia remains unclear. This study first compared the expression of Cyr61 and fibrosis markers (TGF-β1, collagen type I and III) in skeletal muscle of young and old mice. In vitro, D-gal-induced C2C12 aging models were used to assess Cyr61 and Wnt signaling pathway by proliferation/apoptosis assays, ECM analysis, and detecting the changes of myogenic/fibrotic markers (MyoD, α-SMA). Pathway modulation (FH535 inhibitor/LiCl activator) and combined with Cyr61 overexpression and knockout experiments defined mechanistic roles. Cyr61 was upregulated in skeletal muscle of aged mice, which was positively correlated with increased TGF-β1 and collagen deposition. In D-gal-induced C2C12 cells showed suppressed cell proliferation, increased apoptosis and enhanced ECM deposition, accompanied by elevated Cyr61. Cyr61 knockdown or Wnt signaling pathway inhibition (FH535) reversed fibrosis (α-SMA, collagen) and restored myogenesis (MyoD).This study reveals for the first time that Cyr61 drives sarcopenic fibrosis via Wnt/β-catenin activation, promoting myocyte-to-fibrotic transition. Targeting the Cyr61-Wnt axis may ameliorate age-related muscle degeneration, warranting translational validation in preclinical models.Copyright © 2025 The Authors. Published by Elsevier B.V. All rights reserved.