Hollow spheres and capsules have stimulated great interest because of their potential applications in controlled delivery systems, artificial cells, lightweight fillers, catalysis, and as vessels for confined reactions.[1] Hollow spheres, in particular those with complex core–shell structures, have increasingly attracted interest as a result of their superior properties.[ In addition, polyelectrolyte capsules with a shell-in-shell structure exhibit an enhanced mechanical strength and preserved permeability. To date, the synthesis of such complex structures is essentially based on a time-consuming layer-by-layer templating technique, in which layers of desired materials and of sacrificial materials are alternately grown on preformed spheres. Here we report a one-step approach to the synthesis of hollow spheres with a double-shelled complex structure by using commercial polymer hollow spheres as templates. Controlled sulfonation allows the synthesis of templates with tunable thickness of the sulfonated outer layer, sulfonated inner layer, and unsulfonated middle layer. The sulfonation process gives layers with sulfonic acid groups that allow the formation of a wide variety of functional composites. This research provides a novel and efficient approach to the synthesis of various double-shelled functional spheres for many important applications.