Studies worldwide have shown that, besides positive economic and social impacts, labour migrant parents also cause negative effects to the well-being of those they leave behind, especially children. However, this study orientation has not generated significant interest in Vietnam. This article indicates the results of a survey on 469 left-behind children of labour migrant parents in rural areas by comparing them with a control group of 650 children living with their parents in three rural areas of North Vietnam including Phu Tho, Bac Ninh, and Ha Nam provinces. The Keyes's Mental Health Continuum-Short Form (MHC-SF) was used for this study. It is shown that children whose parents work away from home have lower subjective well-being than those living with their parents; children with migrant mothers or with both migrant parents also achieve lower scores of subjective well-being than those with migrant fathers. Factors such as a child's self-assessment of his or her academic and life success and the relationship between the child and his or her migrant parents have significant influence to the child's subjective well-being.