PET fabrics were irradiated by a UV irradiator containing a mercury lamp. The UV-irradiated PET was photo-oxidized by both UV light and ozone and nano-scale roughness was produced on the PET surface. The irradiated PET became less reflective in a visible wavelength region below 450 nm and the zeta potential of the irradiated PET fabric decreased to be more negative compared with that of the pristine PET. The surface modified PET fabric were colored with two cationic dyes. The dyeability of UV treated side increased proportionally with increasing UV energy in comparison with the unirradiated side. Various tone-on-tone patterns were obtained by one-bath dyeing based on the enhanced dyeability of UV-irradiated area on the PET, which is proportional to the UV energy.