Glasses in the system Li2O–SnO–B2O3 system were prepared by a melt-quenching method. Thermal and viscous properties and local structure of these glasses were investigated. The SnO–B2O3 glasses exhibited relatively low glass-transition temperatures (T g) around 350 °C and excellent thermal stability against crystallization. Viscosity measurements in the vicinity of T g indicated that the glasses were considerably fragile compared to alkali borate glasses. Fraction of four-coordinated boron was maximized at the composition with 50 mol% SnO and that of nonbridging oxygen, which is not purely ionic in alkali borate systems but partially covalent, augmented with an increase in the SnO content. Correlation between glass properties and structure was discussed in the SnO–B2O3 binary system.