In midst of growing interest and awareness towards sustainability and being "green", there has been increased demand for sustainable clothing. In the purpose of boosting eco-friendly textiles industry, this research was conducted by investigating environmentally-conscious clothing behavior of university students and assessing their views on eco-friendliness of fibers. Thus, their awareness on recycled polyester fiber was evaluated. The research was conducted by surveying 257 university students residing in Daejeon. The data were analyzed with descriptive statistics, factor analysis, and reliability analysis, using SPSS 19.0. The results were as follows. 1) The majority of the subjects answered "Disposing clothing in the clothing recycling container" to reduce environmental impact. 2) Six factors of eco-friendliness of fiber were extracted as reutilization, unfinishedness, economics, environment preservation, natural materials, and slow fashion by using factor analysis. 3) Subjects scored organic cotton as most eco-friendly among various fibers. Recycled polyester fiber was graded less sustainable than natural fiber, but more eco-friendly than artificial one. 4) In assessment of subject`s awareness of recycled polyester fiber, they highly valued on resource-reutilization and economics, but less valued on its hygiene, thermal insulation and health-functionality.