In this paper, an accurate approximate solutions for 2 problems arising in heat transfer straight fins are presented using optimal homotopy analysis method (OHAM). The approximated solutions are obtained at different values of parameters for the 2 problems are illustrated, and the fin efficiency is also evaluated. Moreover, the 2 problems are of nonlinear convective-radiative conduction and power-law fin-type. The obtained series solutions of OHAM are compared with the numerical solution (using

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... Mathematica solver) and exact solutions. The square residual error is obtained to verify the accuracy of the presented method.