Poly(1,4-butylene adipate) (PBA), poly(l-lactic acid) (PLLA), and poly(d-lactic acid) (PDLA) are biodegradable and environmentally friendly polymers. PLLA- and PDLA-formed stereocomplex crystallites (SCs) by solvent-casting served as nucleating agents of PBA. The isothermal crystallization kinetics and morphology of PBA and 0.23 wt % PBA/SC composites were studied by differential scanning calorimetry, polarizing optical microscopy, and X-ray diffraction. The crystallization rate of neat PBA and PBA/SC composites increased as the crystallization temperature increased. With the addition of 3 wt % SC, the half-time for crystallization of the PBA/SC composite decreased by 2547% for isothermal crystallization at 3844 degrees C compared with that of neat PBA. In the presence of SC, the number of PBA nuclei increased, and the spherulite size decreased substantially. Therefore, the addition of SC to PBA induces heterogeneous nucleation. The product of the surface free energies of the PBA/SC composites is considerably higher than that of PBA because of the presence of amorphous PBA chains that limit the PBA chain flexibility, thereby leading to an increase in the surface free energy.