A vortex theory propeller code was developed and validated using experimental data from a previous full-scale propeller test to analyze propeller performance in icing conditions. The code used propeller geometry and blade section aerodynamic performance data as inputs to compute propeller thrust and power coefficients. After initial validation, the code was applied to a different propeller for which clean and iced thrust data were recently acquired in the McKinley Climatic Laboratory. During the McKinley test, ice accretions were documented, allowing iced blade-section aerodynamic performance data to be obtained experimentally in the University of Illinois 15” x 15” wind tunnel by using ice simulations. These blade-section performance data are discussed in detail in this paper. Using these data, the propeller code predicted thrust and efficiency reductions and changes in required power comparable to those measured in the McKinley test for Appendix C icing conditions. Ice shedding was found to be significant for SLD icing conditions and it is recommended that a shedding model be developed and implemented in the propeller performance code to more accurately predict performance degradation in such conditions.