Building on prior research and theory concerning source evaluation and the role of self‐efficacy in the context of online learning, this study investigated the relationship between teachers' beliefs about their capability to evaluate the trustworthiness of sources and their reliance on relevant source features when judging the trustworthiness of websites concerning special education. We constructed the Source Evaluation Self‐Efficacy Scale (SESES) and used the scores of 263 teachers on this measure to predict their reliance on source features related to the product and the producer of websites when evaluating their trustworthiness. Results showed that even after variance related to gender, age, domain knowledge and frequency of searching the Internet for special education information had been accounted for, teachers' source evaluation self‐efficacy beliefs uniquely predicted their self‐reported use of information about websites' products and producers when judging their trustworthiness. Thus, this research applies self‐efficacy theory and research to a new area and contributes to the burgeoning literature on source evaluation within both reading and information literacy.