Consumption of fast‐food in adolescence is detrimental to mental and physical health. However, data on the temporal trends of fast‐food consumption in this population are scarce, particularly from non‐Western or non‐high‐income settings. Therefore, we aimed to examine this trend in representative samples of school‐going adolescents aged 12–15 years from 18 countries in Africa, Asia, and the Americas, which were predominantly low‐ and middle‐income countries (LMICs). Data from the Global School–based Student Health Survey (GHSH) 2009–2017 were analyzed. Fast‐food consumption referred to eating from a fast‐food restaurant at least once in the past 7 days. The prevalence of fast‐food consumption was calculated for each survey, and crude linear trends within each country were examined by linear regression models. Data on 74,055 students aged 12–15 years were analyzed (mean (standard deviation (SD)) age: 13.9 (1.0) years; 49.2% boys). The mean prevalence of fast‐food consumption was 52.7%. Of the 18 countries included in the study, significant increasing, decreasing, and stable trends were observed in 5, 2, and 11 countries, respectively. The most drastic increases were observed in Morocco between 2010 (44.2%) and 2016 (62.2%) and Lebanon between 2011 (64.6%) and 2017 (77.1%). Significant decreasing trends were observed in Kuwait between 2011 (90.5%) and 2015 (75.1%) and Samoa between 2011 (78.9%) and 2017 (67.3%). The prevalence of fast‐food consumption is overwhelmingly high among adolescents globally. Decreasing trends were only observed in two countries (Kuwait and Samoa). These data suggest that global strategies to tackle fast‐food consumption among adolescents are urgently required.