The composition-dependent behavior of the Dzyaloshinskii–Moriya interaction (DMI), the spin-orbit torque (SOT), as well as anomalous and spin Hall conductivities of Mn1−xFexGe alloys have been investigated by first-principles calculations using the relativistic multiple scattering Korringa–Kohn–Rostoker (KKR) formalism. The Dxx component of the DMI exhibits a strong dependence on the Fe concentration, changing sign at x≈0.85 in line with previous theoretical calculations as well as with experimental results demonstrating the change of spin helicity at x≈0.8. A corresponding behavior with a sign change at x≈0.5 is predicted also for the Fermi-sea contribution to the SOT, because this is closely related to the DMI. In the case of anomalous and spin Hall effects it is shown that the calculated Fermi-sea contributions are rather small and the composition-dependent behavior of these effects are determined mainly by the electronic states at the Fermi level. The spin-orbit-induced scattering mechanisms responsible for both these effects suggest a common origin of the minimum of the anomalous Hall effect and the sign change of the spin Hall effect conductivities.