Biodegradable micelles were fabricated by self-assembly in the aqueous solution of PEG-based ether-anhydride terpolymer consisting of poly(ethylene glycol) (PEG), 1,3-bis(p-carboxyphenoxy) propane (CPP) and sebacic acid (SA). Morphological transition of the micelles was investigated in terms of PEG chain length, hydrophilic–hydrophobic segment ratio, polymer concentration and environmental temperature. The effect of micellar shape on drug loading capacity and cytotoxicity was evaluated. The cellular uptake efficiency was characterized qualitatively with the human hepatoblastoma cell lines (HepG2) and fibroblast normal cells by fluorescence microscopy. Primary in vivo biodistribution of the drug-loaded micelles with diverse morphologies in tumor and normal tissues was also assessed using 4T1 bearing mice. The results show that terpolymer micelles with rod-like shape possess better biocompatibility and the in vivo biodistribution is dependent on micellar shape. Therefore, these polymer micelles have great potential as a novel drug vehicle in nanomedicine.