A convenient one-step method is developed to prepare potentially biocompatible nanocapsules (NCs) with a biocompatible oily core (Miglyol 810, M810), a poly(methyl methacrylate) (PMMA) shell and a dextran coverage. For that, a multi-reactive dextran derivative containing both hydrophobic phenoxy and ATRP initiator groups is used as inisurf (macroinitiator and stabilizer) in an Activator Generated by Electron Transfer-Atom Transfer Radical Polymerization (AGET-ATRP) miniemulsion process. Such dextran inisurfs are shown to efficiently stabilize the direct miniemulsion of MMA with M810 as co-stabilizer, and to confine the polymerization at the oil/water interface via their multiple initiator sites. Grafted copolymers are produced from the inisurf, whose grafts constitute the inner polymeric shell of NCs and are linked to the dextran coverage. The confinement of such polymerization at interface is found to reduce initiator group efficiency, but also to improve both polymerization kinetics and control in comparison with one molecular model initiator. Increasing M810 content promotes the oily core/PMMA shell phase separation during polymerization and the formation of slightly larger NCs, without affecting polymerization kinetics