This paper treats the influence of surface tension on Kelvin-Helmholtz instability arising at the interface separating two superposed, viscous, electrically conducting fluids through a porous medium in the presence of a uniform vertical magnetic field. The stability motion was also assumed to be uniform, and vertical. By applying the normal mode technique to the linearized perturbation equations, the dispersion relation was derived. The stability analysis was carried out for fluids of high kinematic viscosities. It was found that viscosity, surface tension and porosity suppressed the stability, while streaming motion and magnetic field had a destabilizing influence.