Background: Although regular physical activity (PA) can reduce the risk of developing cancer, only one third of adults meet PA guidelines of 150 minutes per week of moderate-to-vigorous intensity PA (MVPA). Knowledge of PA guidelines for the prevention of cancer may provide an important pre-cursor to PA behaviour change. Objectives: We investigated the extent to which adults living in North America are aware of PA guidelines for the prevention of cancer, and whether knowledge of PA guidelines is associated with self-reported MVPA behaviour. Methods: Socio-demographic characteristics, knowledge of PA guidelines for the prevention of cancer, and MVPA behaviour were self-reported by 654 adults (Mage=36.9±14.6 years; 79.1% female) who lived within Canada and the United States in an online survey. Data were analyzed descriptively and using multinomial unadjusted and adjusted logistic regression modeling. Results: Results showed that 49.2% of the sample was aware of PA guidelines for the prevention of cancer. Also, they showed that greater knowledge of PA guidelines was associated with a greater likelihood of being active (unadjusted OR: 1.66, 95% CI: 1.18-2.34; p<.01; adjusted OR: 2.05, 95% CI: 1.36-3.11; p<.01). Conclusion: There is a lack of awareness about the levels of MVPA needed to help prevent cancer. This study gives an indication that those who demonstrate lesser knowledge are also less likely to meet MVPA guidelines. A better understanding of the characteristics of those who are unaware of the guidelines may help in the design of targeted interventions aimed at promoting MVPA to reduce the growing burden of cancer.