A new approach for the estimation of kinetic parameters of crystallization from data obtained during the determination of metastable zone width is presented. The method is based on a simplified dynamic model of the system, which combines the population balance and mass balance, as well as information provided by concentration and particle size distribution measurements using ATR-FTIR spectroscopy and laser backscattering to determine simultaneously the nucleation and growth parameters from the experimental data. The application of the proposed approach is illustrated for the cooling crystallization of paracetamol from water. The technique is compared to existing approaches for the determination of nucleation parameters from metastable zone width experiments and is used to corroborate the assumptions used in the classical approaches. The key conclusion is that the assumptions made in the existing approaches, which simplifies the parameters' estimation procedure, can result in Substantial error in the nucleation kinetics.