Glass samples belonging to the general chemical formula 60Bi2O3–(40-x)MnO2–xZnO with x=5, 10, 15, 20, and 25 mol % are prepared by melt quench method. Characterization of the system was carried out using FT-IR, XRD, SEM and thermal analysis. The structural changes with composition of the glasses have been studied by FT-IR spectroscopy with special reference to structural units of bismuth. Analysis of FT-IR spectra indicate that ZnO is preferentially incorporated into the bismuthate network. Amorphous nature of the system was confirmed by XRD and SEM is used to study the morphology of glass samples. TGA is used to measure the weight loss as the temperature of the sample is increased. DTA is used to identify the glass transition temperature, crystallization temperature and melting temperature.