We address the problem of rationalizing the pattern of fermion masses and mixings by adding a non-Abelian flavor symmetry in a grand unified framework. With this purpose, we include an ${A}_{4}$ flavor symmetry into a unified renormalizable supersymmetric grand unified theory $SU(5)$ model. With the help of the ``type II seesaw'' mechanism we are able to obtain the pattern of observed neutrino mixings in a natural way, through the so-called tribimaximal matrix.