Adolescence is a test of new and different behaviors and part of the natural process of separating from parents, gaining acceptance and popularity with peers, developing a sense of identity, autonomy, independence, and maturity, seeking fun and adventure, and or rebelling against authority. Hence, according to the view of some adolescents, engaging in alcohol, tobacco, and the use of other drugs may be seen as a functional way of achieving independence, maturity, or popularity along with other developmental goals. Cannabis is the most commonly used illegal drug in most countries. Many university students are taking cannabis and other illicit drugs. The main objective of this research was to identify the reasons behind the usage of cannabis among Sri Lankan undergraduates, undergraduates’ attitudes towards the use of cannabis, and Cannabis subculture of undergraduates. The purposive sample included six undergraduates who are excessive users of cannabis. Three participants were from the University of Peradeniya and the other three participants were from the University of Colombo. The study used a qualitative research design comprising of semi-structured individual interviews and the data were analyzed using thematic analysis. The results showed that the most influential reasons to use cannabis were, to reduce stress and anxiety, being an early user, the special feeling felt after using cannabis, to enjoy life and due to the freedom afforded at University; to maintain relationships and to build new relationships with others; to be a hero among others, a perceived increase in academic performance and because cannabis is always available at the university premises. It is important to pay attention to this debilitating issue among our future generations.