Numerical analysis is performed for fluid flows in a supersonic nozzle with cooled walls. The numerical methodology is based on a modified form of the SIMPLER algorithm for compressible fluid, coupled with the scheme developed by Karki et al. for a generalized nonorthogonal coordinate system. The geometry of the supersonic nozzle used for calculations is a two-dimensional convergent-divergent configuration formed by linear walls with a diverging angle of 5° downstream of the throat. Calculations are performed for the conditions where the inlet temperature is 1200 K and walls are cooled and kept at 300 K. The back pressure is set at various values. The adiabatic flows are calculated for comparison. The calculated results for the flow with cooled walls are compared with the experimental data and agree with each other qualitatively.