Polymerization-induced cooperative assembly (PICA) is developed to promote morphological transitions at high solids via RAFT dispersion polymerization, using both a macromolecular chain transfer agent (macro-CTA) and a small molecule chain transfer agent (CTA) to generate nano-objects consisting of well-defined block copolymer and homopolymer. PICA is demonstrated to promote morphological transitions under various conditions. Elemental mapping provides unambiguous evidence for the uniform distribution of the homopolymer within the core of the nano-objects. It is proposed that the growing homopolymer first reaches its solubility limit and forms aggregates, which induce the adsorption of the growing block copolymer. This effective and robust PICA approach significantly expands the capability to promote morphological transitions in RAFT dispersion polymerization and will facilitate the efficient synthesis of various higher-order morphologies at high solids.