This paper deals with an analysis of two-dimensional temperature distribution within a rectangular fin assembly under wet conditions and subject to convective condition at the primary inner wall. An analytical method based upon the separation of variables was suggested to determine the two-dimensional temperature field. A modified one-dimensional model was used to more closely approximate the results of the two-dimensional model; a one-dimensional classical model was also elaborated to provide a basis for comparison, allowing the two-dimensional effect to be established in the case of wet fins. Next, wet fin efficiency was determined. To establish the merit of the present work in considering the two-dimensional effect in wet fins, the results of the two-dimensional model were compared with those obtained from the one-dimensional classical models, demonstrating a considerable difference in their results for various design and psychrometric conditions. The wet-fin analysis presented herein is equally suitable for dry-surface fins by accounting for the absence of latent heat transfer.