Heat transfer processes involving binary- and multicomponent mixtures are ubiquitous in nature, particularly in several industries like the chemical and petrochemical ones. Condensation of binary mixtures inside pipes has been extensively studied during the past decades for unraveling the physical mechanisms controlling heat transfer. In particular, it has been observed that the heat transfer coefficient of mixtures is lower than the ones corresponding to its single–component constituents. This puzzle has motivated a vast research, and this heat transfer deterioration has been attributed to a dominant thermal resistance at the liquid-vapor interface. However, no suitable model has been found to be capable of accurately predicting experimental heat transfer coefficients during flow condensation. We show that the heat transfer deterioration observed during condensation of binary mixtures can be attributed to the change in the physical properties of the multicomponent mixture, and in fact the heat transfer coefficient remains equivalent to the one corresponding to the single-component, contrary to all the existing theories.