This paper reports the first spectroscopic study of free gas-phase ClPO2. Experimental geometric parameters have been determined for the first time and insight into the electronic structure of the molecule has been gained, both from the analysis of the measured Fourier transform microwave spectra. The sample was generated inside a pulsed nozzle by passing an electric discharge through PCl3 and O-2 in He and was subsequently stabilized in a supersonic jet expansion. The determined ClPO2 parameters have been compared with those of related species.