In this paper, we show that the surface tension of charge-stabilized titania suspensions strongly depends on the particle concentration. The surface tension first decreases significantly with an increase in the weight percent and then increases with a further increase in the weight percent. Thermodynamic arguments are used to explain the initial decrease in the surface tension for lower particle concentrations. For higher concentrations, it is hypothesized that the capillary forces acting between the immersed particles at the interface cause the increase in the surface tension.