Professional experience plays a vital role in the formation of teaching self-efficacy (TSE), a construct which has attracted much attention from teacher education researchers. This study investigates how 18 preservice teachers (PTs) reported changes in their TSE for their first professional placement. Data were collected via face-to-face interviews with each PT and analysed in NVivo. Results show the majority of interviewees reported an increase in their TSE after completing the placement. Also, three patterns of individual TSE change were identified: beginning with a low level of TSE before quickly rising to a higher level at the end of the practice, experiencing growth from a medium starting level, and either decrease or increase from an initial high level of TSE. Variations of TSE in subdomains including classroom management, student engagement, instruction, and flexibility were also found. Teacher educators could facilitate PTs' TSE development by providing extra assistance at the beginning of their placements, especially with their classroom management skills.