Isothermal crystallization of the biodegradable homopolymer polyester poly(p-dioxanone) (PDS), and the p-dioxanone copolymer with glycolide PDS-copolymer were studied in situ and in real-time under quiescent or nucleation-enhancing shear conditions. It was found that the spherulitic growth rates remain unchanged with shear, while the nucleation density increases dramatically. Nucleation-enhancing shear conditions, which do not alter the general spherulitic morphology, consist of a short-duration step-shear. This is in contrast to isothermal crystallization under steady-shear conditions, where at low-shear rates, fibrillar crystalline structures form. At high crystallization temperatures, where under quiescent conditions crystal development requires several days, both PDS, and the PDS-copolymer can be made to crystallize in several hours by the imposition of a step-shear.