<p>Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous toxic pollutants that pose significant risks to human health. However, because of their intrinsic non-polar properties, only moderate detection sensitivity can be achieved in the mass spectrometric detection of PAHs. In this work, we presented a novel electrochemically assisted derivatization nano-electrospray ionization mass spectrometry (ECAD-nESI-MS) method to permit the rapid and ultrasensitive analysis of PAHs in complicated samples. In ECAD-nESI-MS, the in situ electrochemical derivatization of PAHs with pyridine and the electrospray ionization are simultaneously activated by applying a high voltage onto the Pt electrode. Notably, the derivatization takes advantage of the inherent electrochemical aspect of electrospray ionization, that is, the electrooxidation of substrates in the positive-ion mode, thus requiring no extra electrochemical cell and potentiostat. Through the electrochemical derivatization of PAHs into the corresponding pyridinium ions, the ECAD-nESI-MS method achieved remarkably improved detection sensitivity, where the limit of detection (LOD) is 3~10 times lower than the state-of-the-art atmospheric pressure chemical ionization mass spectrometry (APCI-MS) and gas chromatography mass spectrometry (GC-MS). With advantages in low detection limit, wide linear range, fast analysis speed (&lt; 3&#xa0;min per sample), and low sample consumption, we anticipate the wide application of the ECAD-nESI-MS method in the rapid and sensitive analysis of PAHs and their analogues.</p> Graphical abstract <p></p>