Young people make up a sizable share of the global population, and most of them reside in developing nations. They consume too much fast food and obesity at a young age is becoming a worldwide epidemic, putting them at risk for nutritional issues from a physiological as well as psychological perspective. Eating fast food has several negative effects on health. Bangladesh's circumstance is not any different. Thus, this study was conducted to identify the level of knowledge on the effect of fast foods on health among young hypertensive patients in Bangladesh. In a tertiary-level cardiology hospital in Dhaka, Bangladesh, 150 young (20 to 35 years old) hypertension patients participated in a descriptive-type cross-sectional study from November to December 2022. Every stage of the study protected the respondents' anonymity, and participants were made aware that they could withdraw from the program at any point while data was being collected. In total, 25.3 percent of respondents had a good knowledge of the impact of fast food on health, compared to 46.0 percent who had moderate knowledge. It was also found that respondents' knowledge level was substantially correlated with their level of education, occupation, and monthly household income. Given this, various measures should be implemented, such as the implementation of health education programs in communities, schools, and universities, to increase the level of public awareness of the effects of fast food on health.