Continuous polymer nanofibers are available through electrospinning, but most have the same structure in their cross section. This article focuses on the fabrication and the structural and mechanical characterization of pencil-like double-layered composite nanofibers coaxially electrospun from solutions of two different biodegradable materials, i.e., gelatin and poly(epsilon-caprolactone) (PCL). Transmission electron microscopy and water contact angle measurements confirmed that a gelatin inner fiber was wrapped with a PCL outer layer. Possible applications of such nanofibers include a controlled degradation rate when used as a medical device in human body. It has been found that the tensile performance of the composite nanofibers was better than those of both the pure constituent, i.e. gelatin and PCL, nanofibers alone. The ultimate strength and ultimate strain of the composite nanofibers with 7.5% w/v gelatin in the core and 10% w/v PCL as shell were at least 68% and 244% higher, respectively, than those of the same concentration pure gelatin and PCL nanofibers. Thus, a coaxial electrospinning technique as used in this article can be applicable, not only in developing functionalized nanofibers but also in elevating their mechanical property. (c) 2005 Wiley Periodicals, Inc.