This pilot randomised controlled trial study investigated the impact of Reading Research to Classroom Practice professional development (PD) on elementary teachers' knowledge of reading skills. This PD, developed by a United States' state education agency, is accredited by the International Dyslexia Association. Teachers (n = 34) were randomly assigned to a treatment or wait-list control (WLC) group and participated in the 5-day, 30-hour in-person PD with up to 10 hours asynchronous application activities. Teachers completed pre- and post-knowledge surveys measuring the impact of the PD on their knowledge related to reading skills. Teachers completed a social validity survey examining their perceptions of the PD. After controlling for pre-test differences, teachers in the treatment group outscored WLC teachers on the knowledge measure at post-test. Following treatment, WLC teachers' growth in knowledge was statistically equivalent to the growth that treatment teachers experienced. Teachers felt the PD improved their knowledge of effective reading practices. Implications for practice and suggestions for future PD are provided.