Shape-controlled block copolymer (BCP) particles that respond to light stimulus have drawn great attention due to their promising applications in smart materials, yet polymeric particles with lighttriggered controllable sequential shape transformation (SST) are still rarely reported. By confined co-assembly of polystyrene-bpoly(2-vinylpyridine) (PS-b-P2VP) and azo-containing lightresponsive additives within emulsions, herein, we fabricated BCP particles with light-controlled SST behavior. Attributed to the quaternization of P2VP chains with bromoalkyl additives and the trans–cis isomerization of an azo group under UV light, the interfacial interactions between the BCPs and the surrounding aqueous phase are significantly varied; therefore, the particles exhibit three distinct phases in sequence: (1) elongation of ellipsoidal particles with increasing domain spacing; (2) shape transformation of elongated ellipsoidal particles into accordion-like particles; and (3) disassembly of polymer particles into small spheres. In addition, these particles with SST behavior can be used in light-controlled drug release at a high spatial–temporal resolution, demonstrating their potential in clinical settings and biomedicine.