The detection of C2 radicals in a premixed acetylene-oxygen flame by using polarization spectroscopy is reported. The signal was recorded in the Swan system, d3IIg-a3IIu (0, 0), using a pulsed dye laser. The spectrum shows a very good signal-to-noise ratio with clearly resolved rotational structures of the P and R triplets. The dependence of the signal on the pump-beam polarization was also studied. The spatial distribution of the signal from C2 radicals in the flame was measured as a demonstration of the use of polarization spectroscopy in combustion diagnostics.