Despite the well-known anticancer activity of mono- and multinuclear platinum complexes, studies of the antitumor performances of platinum-based supramolecular coordination complexes are rare. Herein, we report on the synthesis of a four-armed amphiphilic copolymer, Pt-PAZMB-b-POEGMA, containing a metallacycle M, in which the tetraphenylethene derivative acts as an aggregation-induced emissive fluorescent probe for live cell imaging and the 3,6-bis[trans-Pt(PEt3)2]phenanthrene (PhenPt) is an anticancer drug. This copolymer was further self-assembled into nanoparticles of different sizes and vesicles depending upon the experimental conditions. The impacts of the morphology and size of the assemblies on their endocytic pathways, uptake rates, internalization amounts, and cytotoxicities were investigated. The self-assemblies were further employed to encapsulate doxorubicin (DOX) to achieve a synergistic anticancer effect. Controlled drug release was also realized via amphiphilicity changes and was driven by a glutathione-induced cascade elimination reaction. The DOX-loaded nanoparticles of around 50 nm in size exhibited an excellent antitumor performance as well as a low systemic toxicity, due to an enhanced permeability and retention effect.