Many countries do not include the normal distribution concept in their middle school mathematics curriculum, but on the grounds that middle school mathematics teachers need to know more than just mathematics, researchers argue that preservice teachers (PTs) ought to have knowledge and skills in this area. This study was aimed to investigate PTs' subject matter knowledge (SMK) about the normal distribution. Data was collected from 120 PTs attending a state university through a questionnaire. PTs were asked to evaluate a variety of examples of the normal distribution. The data were analyzed using descriptive statistics and item-based analysis. It was found that the PTs were more knowledgeable about the features of the normal distribution than about standard deviation. Real-life situations made it difficult for them to interpret the concepts associated with normal distributions. Normal distribution curves were more easily interpreted by the PTs. It was determined that their mistakes were the result of their not establishing connections between statistical concepts, and their operational evaluation of concepts. Additionally, PT errors were caused by failure to establish a relationship between probability values and the area covered by the curve and making errors in operation.