Vibrational sum frequency generation (VSFG) spectroscopy is a widely used probe of interfaces and, having ideal surface sensitivity and selectivity, is particularly powerful when applied to wet and soft interfaces. Although VSFG spectroscopy can sensitively detect molecular details of interfaces, interpretation of observed spectra has, until recently, been challenging and often ambiguous. The situation has been greatly improved by remarkable advances in computational VSFG analysis on the basis of molecular modeling and molecular dynamics simulation. This article reviews the basic idea of computational VSFG analysis and recent applications to both aqueous and organic interfaces.