Star‐shaped aliphatic polyesters with hyperbranched cores were prepared by a two‐step synthesis with the one‐pot, arms‐first core method. First, the polymerization of ε‐caprolactone (CL) or L,L‐lactide (LA) was initiated with aluminum isopropoxide trimer. Then, the resulting poly(CL)–OAl< or poly(LA)–OAl< living chains were employed as initiators for 5,5′‐bis(oxepan‐2‐one) or 1,6‐dioxaspiro[4,4]nonane‐2,7‐dione) polymerization. A sequence of chain growth and branching reactions led to the formation of starlike macromolecules. The progress of the polymerization was followed with size exclusion chromatography, and the products of the model reaction were also analyzed with matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry.