The influence of mono ethylene glycol (MEG) on nucleation and the resulting polymorphism of calcium carbonate has been studied at supersaturation ratios in the range of 3-10 and temperatures from 25-80 °C in mixed solvents of ethylene glycol and water. The results show that increased concentration of MEG extends the induction time for precipitation of calcium carbonate significantly, even at the same supersaturation level. The interfacial tension with respect to calcite is lowered as the MEG content increases, but this change is not sufficient to explain the wide variation in the observed induction times. MEG also affects the polymorphic abundance in the precipitates. High concentrations of MEG favour the precipitation of vaterite and higher temperatures promote the formation of aragonite. The particle size is remarkably reduced in solvents with high MEG concentration.