This paper reports on a study exploring metacognition in young children. Developing metacognitive skills helps children become responsible and 'thoughtful about their learning' [Chatzipanteli, A., Grammatikopoulos, V., & Gregoriadis, A. (2014). Development and evaluation of metacognition in early childhood education. "Early Child Development and Care," 184(8), 1223] and can improve educational outcomes [Hattie, J. (2012). "Visible learning for teachers: Maximising impact on learning." Abingdon: Routledge]. This paper explores how conducting video-stimulated reflective dialogues with young children about their thinking supported their metacognitive and cognitive development. Performance on a number of standardized tests was compared to that of a control group. Results indicated that the intervention group made more progress than the control group, became better at discussing their thinking and demonstrated an increase in metacognitive behaviours during classroom activities. The results suggest that VSRD with young children is valuable -- as a participatory research tool, but also as a pedagogical strategy to support the development of metacognition and reflection.