There is wide agreement that teacher professional development (TPD) is a necessary element in educational change, especially for the more effective application of technology to enhance learning. The research literature reports many examples of successful TPD but there remain many challenges to wider and deeper success in the variety of different contexts. Discussion by the thematic working group on TPD at EDUsummIT 2015 in Bangkok identified several challenges to successful TPD. This paper discusses those challenges, describes four cases of successful TPD from varied contexts, and derives a model for TPD based on observed commonalities in the cases.