In this paper, the nonlinear differential equation for temperature distribution of convective straight fins with temperature-dependent thermal conductivity is solved by using a new modified decomposition method (MDM) for boundary value problems. In the new MDM the recursion scheme of the solution components does not involve any undetermined coefficients. Using the new method, the temperature distribution and the efficiency of the fin can be expressed analytically as functions containing two fin parameters without any undetermined coefficients, which greatly facilitates parameter analysis. (C) 2012 Elsevier Ltd. All rights reserved.