The dicarbollide ion, nido‐C2B9H112− is isoelectronic with cyclopentadienyl. Herein, we make dysprosiacarboranes, namely [(C2B9H11)2Ln(THF)2][Na(THF)5] (Ln=Dy, 1Dy) and [(THF)3(μ‐H)3Li]2[{η5‐C6H4(CH2)2C2B9H9}Dy{η2:η5‐C6H4(CH2)2C2B9H9}2Li] 3Dy and show that dicarbollide ligands impose strong magnetic axiality on the central DyIII ion. The effective energy barrier (Ueff) for the loss of magnetization can be varied by the substitution pattern on the dicarbollide. This finding is demonstrated by comparing complexes of nido‐C2B9H112− and nido‐[o‐xylylene‐C2B9H9]2−, which show a Ueff of 430(5) K and 804(7) K, respectively. The blocking temperature defined by the open hysteresis temperature of 3Dy reaches 6.8 K. Moreover, the linear complex [Dy(C2B9H11)2]− is predicted to have comparable properties with the linear [Dy(CpMe3)2]+ complex. As such, carboranyl ligands and their derivatives may provide a new type of organometallic ligand for high‐performance single‐molecule magnets.