The purposes of this study was to study the effect of an information program on the anxiety levels of mothers of children undergoing open heart surgery. The subjects were mothers of pediatrics patients postoperative to open heart surgery who were admitted to the Pediatrics Intensive Care Unit at SongklanagarindHospital. Twenty subjects were assigned to a control group and 20 to the experimental group. All subjects were selected by purposive sampling. The intervention used in the study consisted of a leaflet about information and State Trait Anxiety. The data were analyzed by using SPSS program for percentage, mean, standard deviation, dependent and independent t-test. This study found a significant difference in mothers' anxiety levels between the control and experimental groups (p < .05). The conclusion is that intervention program can decrease the anxiety levels of mothers of children who have undergone open heart surgery