[en] We investigate the feasibility of probing anomalous top-quark couplings of Wtb, Ztt-bar, and γtt-bar in terms of an effective Lagrangian with dimension-six operators at future e⁺e^- linear colliders with a c. m. energy √s ∼ 500 - 800 GeV. We first examine the constraints on these anomalous couplings from the Z → bb-bar data at LEP I and from unitarity considerations. We then consider in detail the effects of anomalous couplings on tt-bar spin correlations in the top-pair production and decay with three spin bases: the helicity, beamline and off-diagonal bases. Our results show that the polarized beams are more suitable for exploring the effects of different new operators. For polarized beams, the helicity basis yields the best sensitivity. (author)