Two Keggin Fe13-oxo clusters, [Pr12Fe33(NO3)6(L-van)4(D-van)5(TEOA)12(μ3-OH)12(μ4-OH)12(μ4-O)28(H2O)4]·(ClO4)3·(NO3)·10H2O (1) and [Dy12Fe33(NO3)2(L-van)3(D-van)3(TEOA)12(μ3-OH)18(μ4-OH)6(μ4-O)28(H2O)9]·(ClO4)5·(NO3)6·15H2O (2), where L-van = l-valine, D-van = d-valine, and TEOA = triethanolamine, were prepared by using Ln3+ as a stabilizer. Cluster 1 crystallizes in a chiral space group of C2, while cluster 2 crystallizes in a centrosymmetric space group of Pnma. Dynamic magnetic measurements of 2 under a zero direct-current field reveal that 2 exhibits single-molecule-magnet characteristics with an energy barrier of 18.79 K. Significantly, the formation of the chiral cluster 1 is closely related to the larger radius of the Pr3+ ion.