This is the second part of the investigation on the precipitation of needle-shaped particles. In part I, two particle aspect ratio-dependent correction factors are introduced to describe the effects of non-spherical precipitate shape on precipitate growth kinetics. In this part II, the two factors are integrated into a CALPHAD-coupled multi-component Kampmann–Wagner numerical model to predict precipitation kinetics of needle-shaped metastable particles during aging treatment of an Al-Mg-Si alloy. The predictions are compared with transmission electron microscopy observations on precipitate number density, volume fraction, and size distribution. Improved agreement is reported, and in particular, the shape of the predicted particle size distribution density function becomes more realistic.