Poly (ethylene oxide)-poly (ε-caprolactone) (PEO5k-PCL6.5k, denoted as OCL3) was employed to prepare both worm-like and spherical micelles. Worm-like micelles had an average length of 6-7 μm, and a similar radius to spherical micelles made from the same OCL3 copolymer. Anticancer drug paclitaxel was encapsulated and the loading capacity and efficiency were determined using HPLC. Due to their cylindrical structures, worm-like micelles showed 1.5-2 fold increase in paclitaxel loading capacity than spherical micelles. DSC analysis demonstrated there were no chemical interactions between paclitaxel and its polymeric excipient. Paclitaxel stability in micelles and in vitro release profiles were also evaluated. Loaded with paclitaxel, OCL3 micelles in both morphologies showed 5-fold lower IC₅₀ than commercial Cremophor^� EL paclitaxel formulation and 15-fold lower IC₅₀ than paclitaxel alone against human lung carcinoma A549 cells. In addition, a nearly 2-fold increase of maximum tolerated dose (MTD) in mice was obtained with paclitaxel-worm micelles compared to spherical micelles, which is probably due to the extended circulation of worm micelles in blood and the consequent retarded distribution into major organs. The increased paclitaxel MTD led to better therapeutic effects on tumor shrinkage with higher administrated doses of paclitaxel in in vivo studies. Systemic circulation, organ biodistribution and apoptosis studies showed a promoted circulation of palictaxel in blood, an enhanced permeation and retention (EPR)-based accumulation in tumor, and significantly reduced toxicity in other major organs (p < 0.05) associated with worm micelles compared to spheres. Thus OCL3 polymeric micelles could be used as an improved paclitaxel carrier with enhanced drug potency and reduced toxicity compared to the commercial Cremophor^� EL. Especially, OCL3 worm-like micelles have shown greater potential than spherical micelles of their ability to increase drug loading capacity, MTD, circulation in blood and accumulation in the tumor site, while reducing toxicity to other major organs.