We consider CP-violating effects in the decays tau --> (3 pi)nu(tau) where both the JP = 1(+) resonance a(1), and J(P) = 0(-) resonance pi' can contribute. The interference between the al and pi' resonances can lead to enhanced CP-violating asymmetries whose magnitudes depend crucially on the pi' decay constant f(pi'). We make an estimate of f(pi') with a simplified chiral Lagrangian coupled to a massive pseudoscalar field, and we compare the estimates from the nonrelativistic quark model and from the QCD sum rule with the estimate from the ''mock'' meson model. We then estimate quantitatively the size of GP-violating effects in a multi-Higgs-doublet model and scalar-leptoquark models, by assuming that the rest frame of the tau can be reconstructed for three-prong decays. We find that, while CP-violating effects in the scalar-leptoquark models may require more than 10(10) tau leptons, CP-violating effects from the multi-Higgs-doublet model can be seen at the 2 sigma level with about 10(7) tau leptons for the maximal value of the CP-violation parameter allowed by present experiments and for tire chiral Lagrangian estimate of f(pi') = (1-5) x 10(-3) GeV.