Bio-based polylactide/poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PLA/PHBV) blend fibers have been prepared via the conventional melt-spinning and hot-drawing process. The spinnability was optimized by determining the narrow temperature window for each blend via rheological studies. The blend fibers showed unexpectedly improved heat-resistance and softness along with acceptable tensile properties, which was related to the significantly modified crystallization and orientation of PLA with appropriate PHBV addition. The phase morphology of PHBV evolved from finely dispersed nanoscale domains into a unique co-continuous state with increasing content. Correspondingly, the nucleation of PLA was favored at low PHBV content; both the nucleation and crystal growth of PLA were enhanced at medium PHBV content; and the crystallization and melting of PLA were confined at high PHBV content. This opened up a novel and viable way to break the performance bottleneck of traditional PLA fibers. (C) 2015 Elsevier Ltd. All rights reserved.