Polychlorinated biphenyls (PCBs) in transformer and food oils were measured using gas chromatography combined with multiphoton ionization mass spectroscopy. An ultrashort laser pulse emitting in the far-ultraviolet region was utilized for efficient ionization of the analytes. Numerous signal peaks were clearly observed for a standard sample mixture of PCBs when the third and fourth harmonic emissions (267 and 200nm) of a femtosecond Ti:sapphire laser (800nm) were employed. The signal intensities were found to be greater when measured at 200nm compared with those measured at 267nm, providing lower detection limits especially for highly chlorinated PCBs at shorter wavelengths. After simple pretreatment using disposable columns, PCB congeners were measured and found to be present in the transformer oils used in Vietnam. Display omitted •PCB congeners would be ionized by a process of two-photon ionization at 267 and 200nm.•The ionization energies were predicted to be 8.10–8.59eV for the PCB congeners.•PCBs were detected from the oil samples obtained in Vietnam.•A femtosecond laser emitting at 200nm was useful for sensitive detection of PCBs.