The rovibrational absorption spectrum of the weakly bound cluster CO2-N2O has been observed in the region of the nu(3) CO2 asymmetric stretch (similar to 2350 cm(-1)). Clusters were formed by supersonic expansion of a mixture of N2O:CO2 in a 4:1 ratio using He carrier gas. Approximately 340 lines have been assigned. Both parallel and perpendicular transitions were observed. The ground state rotational constants A, B, and C are 0.293 924(12), 0.058 004(6), and 0.048 400(6) cm(-1), respectively. The quartic centrifugal distortion constants are D-j = 5.03(17) x 10(-7) cm(-1), D-jk = -3.92(9) x 10(-6) cm(-1), D-k = 1.26(2) x 10(-5) cm(-1), delta(j) = 1.61(92) x 10(-8) cm(-1), and delta(k) = 1.77(80) x 10(-6) cm(-1). Ab initio calculations for several CO2-N2O equilibrium structures have been done on the Hartree-Fock self-consistent field level using a 6-311g* basis set, Moller-Plesset MP2 and MP3 calculations were carried out for the two possible slipped parallel configurations of the dimer. The planar slipped parallel geometry with the oxygen atom of N2O nearest the CO2 monomer was found to be the most stable structure. The spectral constants and stabilization energies were compared to those of the CO2 and N2O homodimers. A planar slipped parallel geometry is observed with the O of N2O nearly over the C of CO2. R(cm) and theta are 3.4701 Angstrom and 60.1 degrees, respectively, assuming the CO2 and N2O are parallel to each other.