The idea of maternal participation in caring for newborns in an NICU has been embraced into many hospitals nowadays. However, the caring practices used in NICU often intimidate the mother in performing her role. The purpose of this study is to understand and describe maternal participation in caring for newborns in an NICU. Non-participant observation and in-depth interview were used to collect the data in this qualitative research. 12 Thai mothers of newborns admitted to an NICU of a tertiary hospital in northern Thailand were recruited in this study as informants. Maternal participation is a continuous process, consisting of two phases; the initiation of participation and the best on-going actions for the sake of the baby. Moreover, mothers provided seventeen activities to the baby in both phases. These activities can be divided into two groups based on mothers' intentions: activities intended to give warmth and encouragement to the babies and activities intended to ensure the babies' safety.