In this article, under certain conditions, we prove the regularity for the solutions of an Allen-Cahn phase-field type system obtained as limits of approximate solutions constructed by using a semidiscrete spectral Galerkin method. With the help of this improved regularity, as one compares to previous results, we then derive error estimates for the approximate solutions in terms of the inverse of the eigenvalues of the Laplacian operator. The system under investigation may model the evolution of solidification or melting of certain binary alloys. Copyright © 2012 John Wiley & Sons, Ltd.351214061414Beckermann, C., Diepers, H.J., Steinbach, I., Karma, A., Tong, X., Modeling melt convection in phase-field simulations of solidification (1999) Journal of Computational Physics, 154, p. 468Diepers, H.J., Berckermann, C., Steinbach, C., Simulation of convection and repenting a binary alloy mush using the phase-field method (1999) Acta Materialia, 47 (13), p. 3663Rappaz, J., Sheid, J.F., Existence of solutions to a phase-field model for the isothermal solidification process of binary alloy (2000) Mathematical Methods in the Applied Sciences, 23 (6), pp. 491-513Vaz, C.L.D., Boldrini, J.L., (2011) A Mathematical Analysis of A Non-isothermal Allen-Cahn Type System, , pre-print), accepted for publicationn in the Mathematical Methods in the Applied SciencesMoroşanu, C., Motreanu, D., A generalized phase-field system (1999) Journal of Mathematical Analysis and Applications, 273, pp. 515-540Evans, L.C., (1998) Partial Differential Equations, , American Mathematical Society: ProvidenceLadyzenskaja, O.A., Solonnikov, V.A., Ural'Ceva, N.N., (1968) Linear and Quasilinear Equations of Parabolic Type, , American Mathematical Society: ProvidenceZheng, S., Nonlinear parabolic equations and hyperbolic-parabolic coupled system (1995) Pitman Monographs and Surveys in Pure and Applied Mathematics, 76. , Longman-Wiley: Essex