Worm-like aggregates with a PAA/P4VP complex core and a PEG/PNIPAM mixed shell were prepared in ethanol by the comicellization of poly(ethylene glycol)-block-poly(acrylic acid) (PEG-b-PAA) and poly(N-isopropylacrylamide)-block-poly(4-vinylpyridine) (PNIPAM-b-P4VP) through hydrogen-bonding. The formed aggregates were studied by dynamic light scattering, static light scattering, H-1 NMR, and transmission electron microscopy. The length of worm-like aggregates could be adjusted by changing the weight ratio of W(PNIPAM-b-P4VP)/W(PEG-b-PAA). When the ratio changed from 20 to 150%, the length changed from about 100 nm to several microns, and the diameter stayed almost unchanged at about 15 nm.