The present study investigated the effect of a preventive substance abuse counselling intervention on Greek emerging adults (18-28 years old). It‘s main purpose was to examine changes in emerging adults’ views, knowledge about substances and their group skills after their participation in the intervention; it also examined their perceptions about the group climate created as well as their evaluation of the intervention. The interactive intervention, lasting 30 hours, consisted of topics such as: emerging adulthood, addiction, causes and consequences of substance abuse, prevention and some training on personal and social skills related to substance abuse. Pre and post intervention measurements explored these changes in a sample of 75 University students (38 in the intervention and 37 in the control group). Students in the intervention group reported high levels in the scale of engagement and lower levels in the scales of conflict and avoidance. Their evaluation of the intervention programme overall was very positive. Additionally, results showed that emerging adults’ views about substances changed positively after the intervention. In terms of how much they learned about substances, the results revealed a significantly important change after the intervention, whereas at the same time, members’ group skills improved. It is concluded that such interventions have an impact on emerging adults’ views and knowledge about substances, a fact which reinforces the need for research-based interventions.