OBJECTIVES: The study objectives were to examine: (1) adolescents' media viewing habits, (2) associations with media viewing and self-reported exposure to unhealthy food and beverage advertising and (3) differences in trends among younger and older adolescents in six high and upper middle-income countries. DESIGN: Repeat cross-sectional online survey. SETTING: Australia, Canada, Chile, Mexico, the United Kingdom (UK) and the United States of America (USA). PARTICIPANTS: Respondents to the International Food Policy Study who provided information on all variables of interest in November-December 2019 aged 10-17 years (n=9171). OUTCOME MEASURES: Self-reported exposure to screen-based media (screen time by media channel), use of social media platforms and self-reported location and frequency of exposure to unhealthy food and beverage advertising. RESULTS: The average amount of time spent in front of various screens ranged from 7.6 hours to 10.2 hours across countries per week day, which may include possible viewing of multiple media channels simultaneously. Overall, Instagram was the most popular social media platform (52%-68% by country), followed by Facebook (42%-79%) and Snapchat (28%-52%). The percentage of respondents who self-reported having seen unhealthy food advertisements in the past 30 days was highest on television (43%-69%), followed by digital media (27%-60%) and gaming applications (10%-17%). Self-reported daily exposure to advertising varied between countries for sugary drinks (10%-43%) and fast food (19%-44%) and was positively associated with self-reported screen time. Self-reported exposure to screen-based media and social media platforms differed by sociodemographic characteristics and was higher among older adolescents than younger adolescents. CONCLUSIONS: The important amount of time spent on screen-based media reported by adolescents and large percentage of adolescents reporting social media usage, coupled with high rates of self-reported advertising exposure, support the need for policies to restrict marketing of unhealthy food and beverages appealing to adolescents on screen-based media.