Sedentary behaviour has unique physiological effects, independent of physical activity, and has been associated with increased chronic disease risk. Research objectives were to examine associations between sedentary behaviour and diet quality, body fat % and physical activity in emerging adults. Relationships between sedentary time and physical activity, and body fat % were also tested. Total sedentary time did not significantly predict HEI-C. Total sedentary time was negatively associated with fibre and F&V intake. HEI-C score, fibre and F&V intake were significantly higher in “low” sedentary reporters while physical activity level and TV viewing were significantly greater in “high” sedentary reporters. Total sedentary time was not associated with physical activity level or body fat %. Diet may be a contributing factor to the negative health consequences that have been observed in people who spend most of their day sedentary.