The de Haas–van Alphen effect in dilute alloys of aluminum-manganese has been measured using the field modulation technique at magnetic fields up to 60 kG and temperatures between 1.1 and 4.2 °K. The period, effective mass ratio, and collision parameter of the third zone y orbits were found to increase linearly on alloying. The increase in the collision parameter attributed to the resonant d scattering by the localized states on the impurity atoms was found to be approximately 10 times larger than the increase observed in aluminum alloys with nontransition element impurities. The effective mass ratio was shown to be enhanced by the electron–phonon interaction and by the localized spin fluctuations on the impurity sites. The parameters which describe the localized state were calculated from the experimental results in the framework of a renormalized theory of localized spin fluctuations and were found to be in agreement with similar parameters calculated from other physical properties. The de Haas–van Alphen results are consistent with the conclusion that the localized state of manganese impurities in aluminum are nonmagnetic but strongly enhanced by localized spin fluctuations.