Despite evidence of quality teaching in Science, Technology, Engineering and Mathematics (STEM) subject domains and insistence on the part of many national governments on the economic value of STEM, education, recruitment and retention into STEM subject fields and occupations is said to be continually blighted by a "leaky pipeline". In the UK context, schools are seen to benefit from a multitude of external STEM engagement and enrichment providers and initiatives. However, despite evidence of the positive impacts of STEM engagement on learners, there exists a dearth of understanding related to how principles of STEM engagement can facilitate STEM teachers in becoming more pedagogically innovative and relevant and, therefore, engaging of their learners in the classroom context. In this article, we employ a secondary data analysis of two prominent cases of public engagement in science and technology (PEST) in the UK to elicit combined lessons for STEM engagement and the pedagogical development of teachers. We consider the successes of science dialogue in establishing principles of best practice that might be transposed to the development of teachers as more able and effective in the engagement of learners in STEM.