The purpose of this study was to understand the relationship between teachers’ self-efficacy and the instructional use of formative assessments in the classroom.Teachers’ efficacy beliefs about their abilities to teach students have an influence on their instructional decisions. Furthermore, effective teaching strategies will help shape the students’ mastery experiences and thus influence the students’ own efficacy beliefs. Teachers were asked to self-rate their own use of formative assessments with students by completing a rubric, which included the following categories: formative assessment frequency, frequency of conferences with small student groups, frequency of student goal setting meetings, and frequency of the teacher requiring students to self-reflect and adjust learning goals. Furthermore, principals rated each responding teacher, using the same criteria as the teachers’ self-rating. Finally, the teachers were asked to complete the Teachers’ Sense of Efficacy Scale (TSES). The TSES provided an overall efficacy rating comprised of three sub-constructs: management, engagement, and instruction. In comparing the teacher and principal TSES responses, there was found to be a strong positive correlation between teachers’ efficacy beliefs and their use of formative assessments. Additionally, my results demonstrated that professional development and building assignment were connected to teachers’ efficacy beliefs. Further exploring these results could have the potential to help teachers and principals become more effective in their practices.