A finite element analysis of a crossflow tube-fin compact heat exchanger is presented. The analysis takes into account the combined effects of one-dimensional longitudinal heat conduction through the exchanger wall and nonuniform inlet fluid flow and temperature distributions on both hot and cold fluid sides. A mathematical equation is developed to generate different types of fluid flow/temperature maldistribution models considering the possible deviations in fluid flow. Using these fluid flow/temperature maldistribution models, the exchanger effectiveness and its deterioration due to the combined effects of longitudinal heat conduction and flow/temperature nonuniformity are calculated for various design and operating conditions of the exchanger. It was found that the performance deteriorations are quite significant in some typical applications due to the combined effects of longitudinal heat conduction: temperature nonuniformity and fluid flow nonuniformity on crossflow tube-fin heat exchanger.