Children with developmental delay are those who at least one of the five aspects is abnormal, including cognitive development, physical development, language and communication development, psychosocial development and self-care skill. Most of the causes of developmental delay are unknown and there is ineffective way for curing. Therefore, it is important to begin intervention as soon as possible in reducing or preventing secondary disabilities. The purposes of this article present the definition and etiology of developmental delay, the importance of early intervention, how to early detect children with developmental delay, and the role of the health professionals in early intervention.