<p>Carbon-containing polymer composites integrated with metal oxide nanoparticles offer opportunities to regulate thermal and magnetic responses through interfacial interactions. This study develops Fe₃O₄/polycaprolactone (PCL) composite microspheres constructed from a carbon-containing biodegradable matrix, enabling magnetically guided chemoembolization and hyperthermia. The microspheres are fabricated <i>via</i> a water-in-oil-in-water emulsion method, resulting in a controlled size distribution (350–550&#xa0;μm) suitable for embolization. Fe₃O₄ nanoparticles are incorporated to confer magnetic responsiveness and photothermal activity, while the carbon-rich polymer matrix (PCL) provides biodegradability and cost-effectiveness. Comprehensive physicochemical characterization confirms the successful integration of Fe₃O₄ and homogeneous morphology of the microspheres. The resulting microspheres exhibit adequate magnetization (6.6 emu g^− 1), photothermal heating capability under near-infrared laser irradiation (ΔT = 4.5&#xa0;°C at 50&#xa0;mg mL^− 1) and dose-dependent embolization behavior in a phantom model. Drug release experiments reveal a biphasic release profile, with an initial burst release (cumulative release of ~ 13% within 3&#xa0;h), followed by sustained release reaching approximately 19%. Thermal analysis revealed a narrowing of the derivative thermogravimetry (DTG) peak relative to neat PCL, suggesting synchronized degradation behavior associated with carbon–metal oxide interfacial interaction. These findings demonstrate that Fe₃O₄/PCL composite system exhibits coordinated magnetic–thermal functionality governed by the carbon-containing polymer matrix and its interfacial interaction with iron oxide nanoparticles.</p> Graphical abstract <p></p>