The aqueous self-assembly of block copolymer systems is of major interest to prepare well-defined nanosized structures. Recently, the self-assembly of well-defined triblock and tetrablock ter- and quarterpolymers into sophisticated multicompartment micelles was reported. Inspired by these examples, the sequential one-pot synthesis of tetrablock ter- and quarterpolymers via living cationic ring-opening polymerization of 2-oxazolines was investigated under microwave irradiation, leading to well-defined tetrablock ter- and quarterpoly(2-oxazoline)s for the first time. The resulting tetrablock ter- and quarterpolymers were analyzed using both size exclusion chromatography and H-1 NMR spectroscopy, revealing their successful preparation. In addition, the surface energy of the polymers was determined to investigate the effect of block order on the surface properties. The last part of the paper discusses the aqueous self-assembly of the tetrablock ter- and quarterpolymers. Atomic force microscopy, transmission electron microscopy, and dynamic light scattering revealed the presence of spherical micellar aggregates.