OBJECTIVES: Non-use of contraception is an important contributor to unintended pregnancy. This study assessed non-use of contraception and its determinants among Canadian youth aged 15 to 24. METHODS: Data from the 2009-2010 Canadian Community Health Survey respondents aged 15 to 24 were used to identify non-users of contraception among heterosexual youth who had had intercourse within the previous 12 months, were not pregnant or sterilized, and felt it was important to avoid pregnancy. Sociodemographic, behavioural, and geographic factors were compared for non-users and users of contraception. RESULTS: Among youth at risk for unintended pregnancy, 15.5% were non-users of contraception. There were no differences between sexes. Across regions of Canada, Quebéc had the highest proportion of at-risk youth, but at-risk Quebéc youth were the least likely to be non-users (7.4%; CI 5.7%-9.0%) compared with at-risk youth in the Territories (28.3%; CI 21.6%-35.0%). In the multivariable analysis, aside from residence outside of Quebéc, younger age, lower income, Aboriginal identification (adjusted OR [aOR] 1.67; CI 1.18-2.37), and smoking (aOR 1.55; CI 1.24-1.92) were associated with non-use. Canadian-born youth (aOR 0.61; CI 0.39-0.96) and those enrolled in school (aOR 0.63; CI 0.50-0.81) were less likely to be non-users. CONCLUSION: The 15.5% of Canadian youth at risk for unintended pregnancy who were non-users of contraception represent an estimated 300 000 Canadian youth. Policies and programs to promote and support access to sexual health services and effective contraception with specific attention to supporting the needs of younger teens, Aboriginal youth, newcomers, low-income youth, and youth who are not in school are needed.