The present thesis investigated the development of episodic memory through middle and late childhood, and how individual differences in health and lifestyle impact this development. The first study (Chapter 2) explored the developmental patterns of episodic memory including individual content elements (what, where and when) and integrated what-where-when (WWW) representation on British children aged 6-12. Results suggest that episodic memory continues to develop during this period, with item, spatial, temporal and WWW memory all improving relatively linearly with age. These improvements are driven by both associative binding and strategic control abilities. The second study (Chapter 3) extended this work by additionally exploring how variation in encoding and strategy use influences memory development in a slightly older age range of 8-13. While associative and strategic retrieval abilities showed improvement with age, strategic encoding ability seemed to stay relatively stable across this period of late childhood. Regarding the effect of strategy use, older children produced and noticed more strategies than younger children, but only the younger children benefitted more from noticing the strategies. The third study (Chapter 4) extended the developmental pattern to a diverse population by replicating the experiment with a sample of Chinese children aged 8-10. Results from Chapters 3 and 4 also indicate that executive function is likely to play a critical role in memory development. The fourth study (Chapter 5) investigated the influences of health and lifestyle factors, with particular emphasis on diet and physical activity, on memory development. The fifth study (Chapter 6) went further in trying to understand how cross-cultural differences in lifestyle may contribute to different patterns of memory development. Results from Chapters 5 and 6 suggest that individual differences in diet and exercise are linked with detectable differences in memory development, and that these effects may not be mediated by executive function. Collectively, the findings of this thesis shed light on a general pattern of episodic memory development over diverse populations across different cultures, and highlight the importance of a healthy lifestyle in promoting children’s cognitive and memory development.