Naturally colored cotton, in accordance with currently increasing interest in ecological textile products and methods, has increased in popularity. Commerce is another of the primary reasons along with interest in environmentally friendly and niche-concept approaches. However, the color palette is limited; no bleaching or dyeing process is used. Instead, only a pretreatment to make the fibers hydrophilic is necessary. This can be induced with several different methods. In this respect, atmospheric-plasma treatments have emerged as an alternative. In this study, knitted and naturally colored cotton fabrics were treated with argon and air atmospheric plasma. The hydrophilicity, wickability, surface friction coefficient, air permeability, water vapor permeability, thermal conductivity, thermal resistance, and fastness were investigated. The surfaces of untreated and plasma-treated fabrics were analyzed with Fourier transform infrared/attenuated total reflectance and scanning electron microscopy to detect and compare the chemical and morphological modifications. The results revealed that atmospheric-plasma treatments are capable of modifying the surface of naturally colored cotton fabrics without any important loss in the color strength or fastness and thermal properties. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 119: 1410-1416, 2011