Electron-beam-irradiated poly(3-hydroxybutyrate) was used as a nucleating agent for poly(3-hydroxybutyrate) in a melt-spinning process. Molecular data and thermal properties of the irradiated samples were determined. The thermal properties of the nucleated melts were determined to assess the influence of the nucleation agents, and then spinning tests were carried out. Thermal and textile properties of the spun fibers were also determined. Estimations of the improvement of the crystallization in the spinline and of the inhibition of secondary crystallization in the fibers from the use of the described blood-compatible nucleation agents are given.