An intrinsic dilemma exists for block copolymer vesicles improving the colloidal stability of vesicles using long/charged stabilizing blocks lowers the propensity of morphological transition to vesicles. Moreover, maintaining the vesicular morphology requires effective structure stabilization via cross-linking. We report a strategy to circumvent this problem and simultaneously improve the colloidal and structural stability of vesicles synthesized via polymerization induced self-assembly (PISA) using dispersion polymerization. More specifically, in situ cross-linked poly(N,N-dimethylacrylamide)-b-poly(diacetone acrylarnide-co-allylacrylamide) diblock copolymer vesicles are first synthesized via aqueous dispersion polymerization, which then serve as a robust platform to initiate the growth of a third hydrophilic block of either neutral poly(N,N-dimethylacrylamide), anionic poly(2-acrylamido-2-methyl-l-propanesulfonic acid sodium salt), or cationic poly(3-acrylamidopropyl trimethylammonium chloride) with retained vesicular morphology. The formed cross-linked triblock copolymer vesicles have advantages of diverse surface chemistry and arbitrary stabilizing block length. As a control experiment, synthesis from linear diblock copolymer vesicles provides a mixture of triblock copolymer vesicles and spheres. The successful synthesis of triblock copolymer vesicles with a binary mixture of two hydrophilic stabilizing blocks is supported by dynamic light scattering (DLS), transmission electron microscopy (TEM), electrophoresis, and X-ray photoelectron spectroscopy (XPS). Both linear and cross-linked triblock copolymer vesicles are subjected to solvent dissolution, freeze-drying, and surfactant challenge studies, which collectively demonstrate that cross-linked triblock copolymers can maintain their vesicular structure and show excellent colloidal and structural stability, as indicated by DLS, TEM, and transmittance measurements.