In this study, we explored early childhood and elementary preservice teachers' science and mathematics teaching efficacy to elucidate pathways to improve teacher preparation programs. Quantitative survey and open-ended responses data were collected from 180 preservice teachers from four universities in the United States. Multilevel ANCOVA and regression suggested that the number of science and mathematics courses taken by preservice teachers was associated with teaching efficacy beliefs, but not with outcome expectancy. Together with evidence from open-ended responses, we argue that besides science and mathematics content courses, preservice teachers also need pedagogical knowledge, hands-on teaching experiences, specialized training opportunities (e.g., workshops), and teaching-related resources (e.g., curriculum, technology) in order to increase the confidence in their potential impacts on students' science and mathematics learning.