This article explores teachers' self-reported learning experiences and core features of the teacher professional development (TPD) programme within a pilot reform project in Armenia. A qualitative exploratory methodology was employed, and the data were generated via survey and semi-structured interviews. Using inductive thematic analysis with elements of abductive reasoning, the study revealed three categories of teachers' learning experiences: (i) development of new modes of learning, (ii) changes in instructional practices, and (iii) attitudinal changes. The study also identifies seven core components of the TPD: (i) active learning, (ii) mentoring, (iii) subject focus, (iv) engaging with and in research, (v) duration, (vi) engagement in the professional learning community, and (vii) collective participation that fostered teachers' learning by providing new insights for designing and implementing TPD programmes. The data analysis shows evidence that the teachers' learning experiences and the components of the TPD programme are interrelated, as most of the learning experiences were reflected in specific programme components.