In a field-induced single-ion magnet [(dtc)₃Dy(phen)] (dtc⁻ = diethyldithiocarbamate anion), replacing two of the S-based dtc⁻ ligands with O-based dbm⁻ ligands (dbm⁻ = dibenzoylmethanoate anion) leads to a significant enhancement of magnetic anisotropy, yielding a rarely reported sulfur-ligated lanthanide-based single-ion magnet [(dbm)₂Dy(dtc)(phen)]. Ab initio calculations reveal that the g_z value of [(dbm)₂Dy(dtc)(phen)] is much larger than that of [(dtc)₃Dy(phen)], consistent with the experimental results.