Introduction of a fluorine-containing block into block copolymers is an effective method to tune block copolymer nanoassemblies with a microphase-separated structure. However, this microphase-separated structure is difficult to clearly observe due to its nanoscale size. In this work, fluorine-containing ABC triblock copolymer vesicles of poly(ethylene glycol)-block-poly-styrene-block-poly(4-vinylbenzyl pentafluorophenyl ether) (PEG-b-PS-b-PVBFP) are synthesized by reversible addition-fragmenta-tion chain transfer (RAFT) polymerization under dispersed condition. Owing to the choice of a suitable degree of polymerization of the three blocks, the synthesized PEG45-b-PS197-b-PVBFP233 vesicles have a relatively large size of around 216 nm and a thin vesicular membrane with a thickness of around 28 nm. Ascribed to the relatively large size of the vesicles and the thin vesicular membrane, it is concluded that the fluorine-containing PVBFP block forms 9 nm columnar microdomains shielded by the PS phase in the vesicular membrane.