The research literature indicates that self-regulated learning can strengthen teacher agency in taking charge of their own learning and teaching, which is important when teachers encounter difficulties or challenges due to the requirements of educational and curriculum reform. This study explores how professional teacher development training activates rural teachers' agency in transforming their practice and becoming self-regulated practitioners in China. Data were collected from two teacher mentors and seven primary school teachers, including classroom observation records, teachers' narratives and reflections, and individual interviews. These participants' self-regulated learning was found to develop through three phases: goal setting and assimilation; implementation of the teaching goal and the teaching methods being learned; and self-reflection. This process intertwined with and reciprocated other-regulated learning. The teachers' agency shifted from initial resistance to adoption of the training, and then to innovation in practice, during which both their cognition and practices were transformed. Implications for teacher learning programs were also discussed.