PLLA crystallization rates increase with nHA content owing to increased nucleation, which compensates a decrease in spherulite growth rate, G, at 100 to 130 °C, and to suppression of the twin peak in G(T) seen in pure PLLA, linked to a transition from the α phase to the disordered α’ phase as T decreases. The decrease in G(T) reflects an increase in viscosity, but nHA may also favour the α’ phase, with consequences not only for the crystallization kinetics but also for resorbtion rates.