A two-phase loop to measure the condensation heat transfer coefficient of R-410A was designed, built, and calibrated. The test section was a 3 m long horizontal, rectangular brass tube 12.7 mm wide and 25.4 mm high. Uncertainty analysis was performed for each set of collected data. Using an experimental database, a correlation was developed to predict the regionally averaged condensation heat transfer coefficient. The effect of oil contamination on the heat transfer performance of condensing R-410 was also investigated.