Zein and zein/poly-L-lactide (PLLA) nanofiber yarns were prepared by Conjugate electrospinning using coupled spinnerets applied with two high electrical voltages of opposite polarities in this article. Structure and morphology of zein yarns were investigated by SEM and X-ray diffraction. The results showed that zein yarn consisted of large quantity of fibers with diameters ranging from several hundreds nanometers to a few microns, and zein concentration played a significant role on the diameter of nanofibers in yarns. To improve mechanical property of nanofiber yarns, PLLA was then incorporated with zein. Zein/PLLA composite nanofiber yarns conjugate electrospun from solution with concentration of 7.5% (zein, w/v)/7.5% (PLLA, w/v) exhibited tensile strength of 0.305 +/- 0.014 cN/dtex. The composite yarns showed better nanofiber alignment along the longitudinal axis. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 114: 2079-2086, 2009