Transarterial embolization is a minimally invasive procedure to selectively deliver embolic agents using a catheter into arteries to occlude diseased or injured vasculature for therapeutic intent. In this study, a decellularized cardiac extracellular matrix (ECM)–based nanocomposite gel is developed to provide outstanding mechanical stability, catheter injectability, retrievability, antibacterial properties, and biological activity to prevent recanalization. The malleable and shear-thinning nature of the nanocomposites gel allows the formation of an impenetrable solid cast to fill various vessel geometries and sizes, avoiding recurrent bleeding, and provides the versatility that cannot be achieved by clinically used agents. The embolic efficacy of gel is shown in a porcine survival model of embolization in the iliac artery and the renal artery. With its proregenerative, antibacterial properties coupled with favorable mechanical properties, the bioactive ECM–based nanocomposite gel enables wide tunability as the next-generation embolic agents with the potential to treat a broad range of vascular diseases.