Introduction: This study offers insights into Dutch young people's expected social and personal consequences of ecstasy use. Substance use expectancies are assumed to be an essential component in explaining substance use behaviour and, therefore, the development of effective substance use prevention and treatment strategies. Method: Dutch young adults with an online interest in drug-related social media posts were targeted with an online survey about their use of alcohol and drugs. This resulted in a convenience sample (N = 4182, 73.4% female, Mage = 21.11), of which 35.5% had used ecstasy at least once in their life and 29.3% had used ecstasy last year. Latent class analyses were used to identify subgroups based on both positive and negative expectancies of ecstasy use. Cross-class differences were examined using multinomial logistic regression. Results: This study yielded four distinct classes: only negative expectancies (13.6%), high positive and negative expectancies (23.5%), low to moderate positive and negative expectancies (20.6%), and mostly positive expectancies (22.4%). These classes differed significantly in lifetime experience with ecstasy use, intention to use ecstasy, perception of harmfulness and availability, and social norms regarding the use of ecstasy. Conclusion: Findings show that ecstasy use expectancies can be used to create meaningful classes of users and non-users, and that these classes are different enough to warrant varied prevention approaches. Expectancies young people have regarding the use of ecstasy are associated with various ecstasy use-related variables and should be taken into consideration when developing and implementing preventive interventions.