In the presented work, Sc3.1In, a weak itinerant ferromagnet with no magnetic constituents, is doped with Er3+ local moment ions, to form (Sc1−xErx )3.1In. As x increases, theWeiss-like temperature θ stays positive and nearly triples up to x = 0.10. Moreover, Er doping of as little as x = 0.02 induces a cluster-glass state, which persists up to x = 0.10, as evidenced by dc and ac susceptibility measurements, and confirmed by the Vogel-Fulcher Analysis.