We present X-ray observation of the old nova CP Puppis obtained by the ROSAT Position Sensitive Proportional Counter in 1993 April. The source is detected with a count rate of 0.067 +/- 0.004 counts s-1. The total observed X-ray flux between 0.1 and 2.4 keV is ~3 x 10-12 ergs s-1 cm-2. The spectrum of the source is best fit by a thermal bremsstrahlung emission model with temperature >=1 keV. The X-ray count rates are modulated with the previously known spectroscopic period ~0.d0614 (~88.4 minutes) of the system at the 3 sigma confidence level. The hard X-ray flux and the detected X-ray modulations suggest that CP Puppis is an intermediate polar system.