We extend Teixeira and Telo da Gama's density-functional approach [J. Phys.: Condens. Matter 3, 111 (1991)] to study the vapor-liquid phase equilibria and planar interfacial properties of quadrupolar fluids. The density profile, surface ordering, surface polarization, and surface tension of quadrupolar fluids are evaluated. Particular attention is given to the temperature and quadrupole-strength dependence. It is found that the interfacial molecular ordering can arise entirely due to the quadrupole-quadrupole interaction. It is also found that the bulk-phase properties of the quadrupolar fluids satisfy the law of correspondence states. The reduced surface potential and surface tension can be well correlated by power laws of the scaled temperature tauequivalent to1-T/T-c, where T-c is the critical temperature of the fluids.