In this paper, I explore preservice science teachers’ (science PSTs’) reflective practice (RP) during a 1-year Postgraduate Certificate in Education programme in England. Previous research suggests that science PSTs are not very reflective, and I hypothesised that lack of reflectivity is related to their difficulty in learning to teach. Science PSTs (n = 38) took part in a teaching intervention designed to support development of RP, and eight volunteered as research participants. Four seminars about the diagnostic teaching cycle and action learning (AL) took place in the university during the year. Data collected included written reflective journals, analyses of critical incidents, and action plans; audio recordings of AL sets; and school-based mentors’ reports of participants’ progress in school placements. I investigated participants’ reflectivity using Zwokdiak-Myers’ nine dimensions of reflective practice. There was substantial variation between participants, and more evidence of reflectivity in some dimensions than in others. A relative strength was that participants adopted a range of teaching strategies (Dimension 6), but linking theory with practice (Dimension 3) was a weakness.