The Supervised Agricultural Experience (SAE) program is a valuable component of school-based agricultural education (SBAE). SAE component outcomes consist of real-world career exposure and skill development through experiential learning. Unfortunately, the SAE program is often the weakest component of SBAE in local programs. As such, SBAE teachers regularly request professional development in supervising student SAE projects. To address this need, we evaluated preservice teachers' self-efficacy for teaching SAE throughout a semester-long course focused on the topic. We were especially interested in how self-efficacy changed over time, and we used an explanatory mixed-methods approach to do so. Our findings revealed that preservice teachers increased their perceived SAE self-efficacy by one full point on a 5-point scale, as a result of the course, when comparing data from Week 1 to Week 16. Financial data records of SAEs were perceived as the lowest SAE self-efficacy item for preservice teachers. Focus group members identified mastery experiences in the form of experiential learning and vicarious experiences of course instructors as contributing factors to their increase in SAE self-efficacy. It was recommended to course instructors to continue experiential learning projects and employing current and previous SBAE teachers as course instructors and guest speakers while also revising instruction related to The Agricultural Experience Tracker. Peer institutions should consider an experiential learning experience in relation to SAE supervision in their SBAE teacher preparation program.