Addition of donor ligands such as pyridine N-oxide or 2-methylimidazole to the chiral (salen)manganese(III) complex catalyzed asymmetric epoxidation of unfunctionalized olefins was found to be effective for altering the enantioselectivity and the chemical yield. The highest asymmetric yields were obtained for the respective epoxidation of (E)-1-phenylpropene (56% ee) and 1,2-dihydronaphthalene (83% ee).