Background: Youth consume high volumes of fast food, putting them at risk for poor diet, weight gain and several noncommunicable diseases. Fast food marketing can affect youth's food-related behaviours and has been identified as a determinant of excess weight and obesity. The aim of this research is to examine the relationship between exposure to fast food marketing and the fast food brand preferences and intake amongst youth aged 10-17 across six countries. Methods: The International Food Policy Study youth survey collects data on dietary patterns and behaviours amongst youth aged 10-17 living in six countries. Data on fast food marketing exposure, brand preferences and intake were compared using regression models adjusted for age, sex, income adequacy and ethnicity. Results: Exposure to fast food marketing was positively associated with both brand preferences and fast food intake across most countries. Brand preferences were consistently high across all countries when exposed to brand-specific marketing. Fast food intake was higher amongst ethnic minority respondents than ethnic majority respondents and amongst males compared to females. Conclusion: Fast food marketing is consistently associated with brand preferences and intake across all countries investigated, which points to the need for stringent government regulation to reduce unhealthy food marketing to youth in all 6 countries.