Factors such as high viscosity of sugar solutions or multicomponent systems with flavoring agents complicate the crystallization of sugar in the food industry. The influence of caffeine on the crystallization behavior of sugar solutions was tested. The determined parameters were solubility, metastable zone width, nucleation, crystal growth rate, and shape of crystals. For the metastable zone two different concentrations were tested. The crystal growth rate was determined at two temperatures as well as at two supersaturations. The results indicate that caffeine affects the crystal growth rate and metastable zone. The crystal growth rate is decreased and the saturation line as well as the nucleation line is shifted to lower temperatures caused by a thermodynamic effect.