Display omitted •The hybrid O3-ECF process was successfully applied to remove phenol.•Two different carbon nanotube (CNT) networks were used as anode material.•Ozone-CNT functionalization and potential O3-ECF mechanisms were discussed.•Residual mass on the CNT electrode was considerably reduced with O3-ECF hybrid process.•Improved kinetic performance was achieved for O3-ECF as compared to the sum of the individual processes. Here, we investigated the synergistic effect towards phenol degradation and mineralization between ozonation (O3) and electrochemical filtration (ECF) using perforated titanium as cathode and porous carbon nanotube (CNT) networks as anode. A flow rate of 1.6 mL min−1, 10 mM of sodium sulfate electrolyte, 1.0 mM of phenol (model aromatic compound), and an ozone dose of 12 mgO3 L−1 were used. Insight into the synergistic mechanism was achieved via carbon anode morphology characterization and phenol degradation kinetics analysis. Improved kinetic performance was observed for the combined process (O3-ECF) as compared to the sum of the individual processes, not only towards phenol degradation (3.2-fold increase), but also towards phenol mineralization (2.2-fold increase). Scanning electron microscopy revealed a significant decrease of polymer formation and deposition on CNT after the hybrid O3-ECF process as compared to the ECF alone. Voltage-dependent (0–2.5 V) ozone CNT functionalization was investigated at pH 7–11 to assist in elucidation of the synergistic mechanism. X-Ray photoelectron spectroscopy indicated increases up to 26-fold in CNT oxygen content post-ozonation at pH 7 comparing to fresh CNT. Various potential O3-ECF synergistic reaction mechanisms for organic aromatic oxidation and mineralization are discussed.