Cold atmospheric pressure plasma (CAP) treatment has been shown to kill bacteria and remove bacterial biofilms from surfaces. Here, we report the etch capacity of a linear discharge CAP device on Pseudomonas fluorescens biofilms. A 21 kHz, 1.4-kV RMS AC voltage applied to the CAP electrodes generated a hydrated Ar plasma between the plates, with the gas flow directing the plasma species toward the biological sample, causing both bacterial killing and etching of the biofilm. Typical discharge currents for a 2.4-cm long, 0.6-mm wide linear discharge device were 1–4.4 mA. Hydrated Ar flow gas was critical for removal of biofilm from a stainless steel substrate, while both hydrated and dry Ar + O2 , Ar + air, O2 only, and air only flow gas mixtures did not cause etching at equivalent or greater discharge current intensities. A biofilm etch rate of > 2 μm/min was achieved, provided the plasma discharge was within 1–2 mm of the substrate surface and used a hydrated Ar gas flow of at least 5 LPM.