This study explored elementary school teachers' familiarity, conceptual knowledge, and interest in learning more about light and its related concepts. This study also sought to establish the relationship between elementary school teachers' familiarity, conceptual knowledge, and interest in learning light concepts. Sixty-six lower and upper elementary school teachers in Midwest of the USA participated in this study. Data were collected using 3 instruments namely Familiarity with Light Concepts Questionnaire, Conceptual Knowledge of Light Test, and Interest in Learning about Light Concepts Questionnaire. Data were analyzed using statistical tests. Most teachers expressed high levels of familiarity with light concepts surveyed. The upper elementary grade teachers expressed more familiarity with advanced light concepts than lower elementary grade teachers. However, most teachers exhibited low conceptual knowledge of light concepts. There was no significant difference in conceptual knowledge of light concepts between lower and upper elementary grade teachers, and between more experienced and less experienced teachers. As such, teachers' self-reported familiarity with light concepts was not consistent with their actual knowledge of the concepts. However, most teachers expressed high interest in learning more about the light concepts. Thus, teachers showed willingness to learn more about light concepts they did not understand. These findings have implications on teacher education, and science teaching and learning.