The tribocharging characteristics of polymer powders have a significant impact on several industrial processes such as electrostatic powder coating and polymer powder processing. The nature of chemical species on the surface of powder influences the triboelectric charging characteristics. An atmospheric-pressure helium plasma was used to modify tribocharging properties of polystyrene microspheres and acrylic powders. Plasma surface modification reduced the magnitude of tribocharging for the test polymer powders. When tribocharged against stainless steel, the net charge-to-mass ratio (Q/M) for both polystyrene microspheres and acrylic powders was less than that for the control samples. Plasma surface modification also reduced the tribocharging of mannitol, a pharmaceutical powder, against stainless steel. Further, Mars simulant dust (JSC Mars 1) was used as a test sample to study the effect of carbon dioxide physisorption on tribocharging. The Q/M of the sample with physisorbed CO2 was less than that of the control in all size ranges.