This paper presents an exploratory study examines environmental knowledge, attitude, behavior and the extent to which they are related among university students in Indonesia. Data collected from students of Andalas University at Sumatra Island, University of Indonesia at Java Island and University of Udayana at Bali Island. The results show that in the scale of 1 to 5 the mean score of environmental knowledge among three university students ranges from 4.380 to 4.460. This range indicates that students have good knowledge about environmental issues. The mean score for environmental attitude ranges between 3.867 and 3.935. In scale of 1 to 5 this range indicate statement of fairly agree with six measurements of environmental attitude. In measurement of regulatory attitude, student’s response ranges from 4.051 to 4.080 which indicate agreement towards stronger enforcement of environmental regulations. While for environmental behavior, students response show range from 3.589 to 3.683 which indicate that they quite interested in five potential actions they can involve in environmental protection. Based on compare mean analysis for all four variables, it was found that there is significant difference among three universities in environmental knowledge, environmental attitude, regulatory attitude and environmental behavior. The results of partial least square model confirmed that environmental knowledge affect environmental attitude, and then attitude affects environmental behavior intention. However, R square of environmental behavior only 0.323 which means there more than two third of decision on behaving environmentally is influenced by other factors.