Previous studies have revealed that "neuromyths," which are misconceptions about the brain, show a high prevalence among teachers in different countries. However, little is known about the origin of these ideas; that is to say, the sources that may influence their presence among teachers. This research aims to identify the prevalence of five frequent neuromyths among teachers in Quebec (belief in neuromyths and reported practices) and the reported sources of these beliefs (e.g., reading popular science texts). A total of 972 teachers from Quebec responded to an online questionnaire. Results show a lower prevalence than previous studies (although it remains high), and that the main sources cited by participants are related to cognitive biases and university training. To our knowledge, this study is the first to report data supporting the idea that cognitive biases are related to the prevalence of neuromyths.