We have used the Owens Valley Millimeter Array to conduct a sensitive search for CO (1 - 0) emission in the radio-loud quasar 3C 48. An emission feature is detected (4σ) at the redshift of the narrow optical emission lines (z = 0.3695). The width of this feature is ~250 km s^-1^(FWHM) similar to that expected for a galactic disk, and the integrated CO line flux implies an H_2_ mass of 7 x 10^10^ M_sun_ (assuming the same CO to H_2_ conversion factor found for giant molecular clouds in the Milky Way). This H_2_ mass is ~30 times that for the Galaxy, and about twice that estimated for ultraluminous IRAS galaxies such as Arp 220 and the UV-excess quasar Mrk 1014. These data support previous suggestions that 3C 48 may have formed from the recent merger of gas-rich galaxies and that the extended nebulosity surrounding the quasar is largely due to a population of young stars which could have been formed from the gas detected here.