This paper presents the first experimental evidence on electroosmotic flow at a liquid-air interface. A PDMS microchannel with an opening to air was created to allow for the formation of a liquid-air interface. Polystyrene particles were used to visualize the liquid motion and the experiments found that the particle velocity at the liquid-air interface was significantly slower than the particle velocity in the bulk. This result agrees with a mathematical model that considers the effects of electrical surface charges at the liquid-air interface in electroosmotic flow.