The first three chiral dodecamanganese clusters that behave as single-molecule magnets are reported. All reveal natural optical activity, which is stronger for the 2-chloropropionate derivative than for either the (S)-6-methoxy-α-methyl-2-naphthaleneacetate or the (S)-2-phenylbutyric acetate compounds. For the cluster with 2-chloropropionate moieties at its periphery, the magnetic circular dichroism was investigated and found to display large optical hysteresis, which depends on the direction in which the magnetic field direction is swept.