The aim of this study was to explore the application of recycling bins to improve waste separation practices of undergraduate students from the Department of Environmental Science in the Faculty of Science at Chulalongkorn University. Bin monsters, waste separation bins shaped like monsters, were created by 11 undergraduate students in the Environmental Science Communication course. The results showed that most participants (undergraduate students from the Department of Environmental Science) had a good working knowledge of waste separation and a positive attitude toward recycling. However, their sorting behavior did not correspond with their knowledge or attitude. To increase their awareness and improve their behavior in solid waste separation, the program should be continued and more bin monsters should be deployed.