A series of unsaturated polyester resins based on 3,6-bis(methoxymethyl)-durene with different diacids or anhydrides, namely, phthalic anhydride, maleic anhydride, and succinic acid, and different glycols, namely, 1,2-propylene glycol, triethylene glycol, 1,4-cyclohexane diol, and 3,6-bis(benzyloxymethyl)durene, were prepared. Infrared and nuclear magnetic resonance spectra were used to characterize the unsaturated polyester resins obtained qualitatively and quantitatively. The average-number molecular weight (M-n(-)) was determined by end-group analysis. These polyesters were found to cure with styrene at room temperature. The thermal behavior of the styrenated polyesters was studied via thermogravimetrical analysis and differential scanning calorimetry (TGA and DSC).