This qualitative study investigates multi-cases of junior high school English teachers to reveal the dissonances between teachers' beliefs and practices of formative assessment in EFL classes viewed from different Continuing Professional Development (CPD). The Data were collected by conducting semistructured interviews to all respondents, classroom observations and document studies such as journals and lesson plans. The result of this study showed that teachers with high CPD participation level have stronger beliefs in formative assessment compared to those with lower CPD involvement. Their beliefs, however, were not always practiced appropriately in the classroom. Teachers' CPD participation has no real impact on the success of formative assessment practices, although it may influence teachers' beliefs. This is due to some factors influenced the implementation of formative assessment in the classroom. Futhermore, it is expected that teachers carefully consider the influecing factors and carry out formative assessment in accordance with their beliefs.