Planar-coil supramolecular block copolymers fabricated from a cationic platinum(II) complex with sulfonate terminated polystyrenes can self-assemble into vesicles, which show further spontaneous fusion, with an hour-scale fusion time, in chloroform–methanol (v/v = 1) mixed solvents. The vesicle fusion intermediates, including docking vesicles, arrow-like protrusions, stalk-like intermediates, hemifusion diaphragms and fusion pores, are clearly imaged by transmission electron microscopy. It is proposed that such a fusion process is triggered by Pt/Pt and p–p stacking interactions between the platinum(II) complexes.