China's rural-urban migration has resulted in 61 million children living apart from their parent(s) in rural communities. Previous studies have failed to examine the long-term effects of parental migration on left-behind children's nutritional health, and have not examined the gender differences (of parents and children) in those associations. This research uses a mixed-methods design that incorporates quantitative and qualitative techniques to explore links between parental migration, care-giving arrangements and left-behind children's nutritional health in rural China. The quantitative analyses draw on a longitudinal dataset - the China Health and Nutrition Survey (CHNS) (1997, 2000, 2004, 2006, and 2009) to examine the relationships between children's nutritional outcomes and different patterns of parental migration including being left behind in different stages of childhood, and being left behind by the father or the mother. The qualitative component consists of analyses of interviews with 32 caregivers (21 grandparents, 9 mothers, and 2 uncles/aunts), and children's diaries (26 children aged 6-12, 21 left-behind children and 5 non-left-behind children) to explore the care-giving practices for left-behind children from the perspectives of a group of children and their caregivers in rural northern central China. Results of the quantitative analyses show negative associations between parental migration, especially maternal migration, and left-behind children's nutritional outcomes indicated by anthropometric measures and macronutrient intakes, and this is particularly true for boys left behind during early life in rural China. The qualitative findings highlight the importance of socio-cultural factors, since there seems to be a paradox of intergenerational obligations for boys in a culture where sons are more valued than daughters. This is because parents migrate to save for their sons' adult lives, reducing the remittances sent to support their sons who stay behind. There is less pressure to save for daughters' adult lives and so more potential for remittances to support their nutrition. The research also recognizes the importance of grandparents as carers, and their experiences and beliefs about healthy eating for children. Grandparents, particularly on the paternal side, are expected to fulfil social obligations to care for left-behind grandchildren even without immediate financial returns. Inadequate financial support from the migrant parents of left-behind boys in rural China, in particular boys cared for by paternal grandparents, may result in greater risk of poor nutrition during the early childhood. This potentially renders such left-behind boys vulnerable to developmental delays. These findings are important for policy-makers to develop effective interventions to improve left-behind children's nutritional well-being in rural China.