Abstract Background Food insecurity is impacted by social determinants of health and is a risk factor for poor nutrition. Simultaneously, nutrition insecurity remains a pervasive public health concern in wealthy countries, especially for children. This study describes characteristics of youth that may increase risk of food and nutrition insecurity. Methods A cross-sectional study of grade nine students took place in 37 schools in Manitoba, Canada. Students completed a web-based survey on food security, diet, and nutrition-related behaviours. When consenting, parents/guardians could provide their child's health number. This sub-sample (n = 943) was linked with social and health variables through a de-identified data repository and used for this study. Bivariate associations explored relationships between sociodemographic information, diet quality, eating behaviours, mental health, and food security. A multivariable logistic regression model determined adjusted odds ratios and 95% confidence limits for food security, and a general linear model for diet quality. Significance was set at p < 0.05 for all analyses. Results Twenty percent of participants were food insecure and 70% had sub-optimal diets. Food security was positively associated with living in a rural area, in higher income neighbourhoods and eating family dinner more frequently, while living in a northern area or in social housing, were negatively associated. Food security was not significantly related to diet quality; however, better nutrition was associated with being female, higher self-rated health, absence of a mental health diagnosis, and more frequent breakfast consumption, while receiving social assistance and living in a northern area were negatively associated with diet. Conclusions While results show a socioeconomic and geographic vulnerability to food insecurity, the diet quality of most adolescents was low. A multidimensional public health approach is needed to resolve these connected yet different issues. Key messages • Food insecurity and nutrition insecurity are public health concerns that require distinct but related interventions. • Scaling up income supports to resolve food insecurity is insufficient to improve dietary quality across adolescent populations.