Kevlar 149 fibers have been surface treated with NH3-, O2-, or H2O-plasma to modify the fiber surfaces. SEM (scanning electron microscopy) is used to characterize the surface topography of fibers etched by gas plasmas. The chemical compositions and functional groups of the fiber surfaces are identified by ESCA (electron spectroscopy for chemical analysis) and SSIMS (static secondary ion mass spectroscopy), respectively. The contact angle of water on modified PPTA [poly(p-phenylene terephthalamide)] film prepared from using Kevlar 149 fibers is also used to investigate the wettability. The results show that the etching abilities of gas plasmas are dependent on the type of gas used for plasma treatments. The contact angle data indicate that all the three gas plasma treatments are effective in rendering the surface of PPTA more hydrophilic. The ESCA analysis results show that the surface compositions of plasma-treated fibers are highly dependent on the type of gas used and treatment time. Changes in surface compositions of fibers treated by NH3-, O2-, and H2O-plasma are observed. Increasing nitrogen and oxygen contents are observed for the NH3-Plasma treatment, and the O2- and H2O-plasma treatments, respectively. Furthermore, the incorporation of amino groups into fiber surfaces by NH3-plasma treatment and the extensive damage of the aromatic ring and the polymer backbone by H2O-plasma and O2-plasma are evidenced by SSIMS.