Pre-service teachers who conduct experiments are faced with various risks in terms of physical, health and environment due to the chemicals they are exposed to in the laboratory classes. Working in a laboratory without knowing these risks causes accidents such as chemical spills, explosions and fires, and even individual injuries. For this reason, pre-service teachers should be trained about the importance of safety and the properties of the chemicals with using various learning strategies. In this context, we aimed to determine the knowledge about lab safety among the pre-service teachers through real-life laboratory accidents. This study, which focuses especially on the role of chemical substances in laboratory safety, was discussed with its various dimensions. 21 pre-service teachers taking the Laboratory Safety course and attending the Chemistry Teaching Program in a state university's the Faculty of Education in Aegean region (Turkey), participated in this research, based on the case study method. Worksheets containing cases related to laboratory accidents and semi-structured interview form were used as data collection tools. Considering the results of the research, we found that the pre-service teachers generally had a lack of knowledge on the chemicals' hazard classifications, physical, health and environmental hazards, pictograms, chemical properties, and safety precautions of chemicals within the frame of laboratory safety.