The release behavior of a water-soluble small molecule drug from the drug-loaded nanofibers prepared by emulsion-electrospinning was investigated. Doxorubicin hydrochloride (Dox), a water-soluble anticancer agent, was used as the model drug. The laser scanning confocal microscopic images indicated that the drug was well incorporated into amphiphilic poly(ethylene glycol)–poly(l-lactic acid) (PEG–PLA) diblock copolymer nanofibers, forming “core-sheath” structured drug-loaded nanofibers. The drug release behavior of this drug-loaded system showed a three-stage diffusion-controlled mechanism, in which the release rate of the first stage was slower than that of the second stage, but both obeyed Fick’s second law. Based on these results, it is concluded that the Dox-loaded fibers prepared by emulsion-electrospinning represent a reservoir-type delivery system in which the Dox release rate decreases with the increasing Dox content in the fibers.