Amorphous carbon (a-C) films have a growing interest in the biological and medical field, as a coating material, due to their biocompatibility and antibacterial property. However, a-C films deposited directly on polymers often show adhesion failure. In this paper, two types of a-C films, amorphous hydrogenated carbon (a-C:H) film and hydrogen-free a-C (H-free a-C) film were deposited on polytetrafluoroethylene (PTFE) using a plasma deposition method. Prior to a-C film coating, the PTFE substrates were treated with Ar and O 2 plasma and an appropriate interlayer was chosen to enhance the adhesion strength. The effect of the plasma pretreatment on the chemical composition of the PTFE was investigated by X-ray photoelectron spectroscopy (XPS). A T-peel test was carried out to evaluate the adhesion strength of the a-C coated PTFE. In the T-peel test, Ar plasma pretreatment improved the adhesion strength more effectively than that of O2 plasma pretreatment, because of the substantial defluorination and oxygen bonding occurred by Ar plasma pretreatment. Moreover, H-free a-C film reduced the numbers of Escherichia coli (E. coli) colonies dramatically, compared with original PTFE and a-C:H coated PTFE. Consequently, H-free a-C film coating can be a promising method to inhibit the increase of bacteria.