Background: Snacks mainly from street food, provide 20–31.1 percent of the energy that students need per day. Street food refers to ready-to-eat food and beverages prepared and served in public areas. In contrast, street food vendors frequently add hazardous substances such as formalin and borax, as well as cyclamate, rhodamine B, and methanyl yellow, which can be harmful to students' health. This study aimed to observing the current condition of street food vendors surrounding the schools in Semarang city. Methods: This was an observational study selected by consecutive sampling. Street food samples were collected from 37 schools in Semarang city, Indonesia. The hazardous substances such as formalin, borax, methanyl yellow, and cyclamate were qualitatively tested using easy testing kits. Result: This study showed that 78.3% of the street food samples had formalin, 19.1% contained rhodamin B, 3.3% included methanyl yellow, and 4.0% contained cyclamate. Conclusion: Street food has a high ratio of preservatives (formalin). Therefore, it is necessary to regulate the sale of street food, especially those containing hazardous food additives.