Parent-child interaction, gratitude and prosocial behavior have a crucial impact on psychological development. According to our literature review, these three variables are positively related to one another. Therefore, the authors created a model that treats parent-child interaction as an exogenous variable, gratitude as a mediating variable, and prosocial behaviors as endogenous variables. To test this model, the authors administered the Parent-Child Interaction Scale, the Gratitude Scale, and the Prosocial Behavior Scale, which have good validity and reliability, to a total of 987 fifth- and sixth-grade students in Kaohsiung. In regard of gender, there were 521 males, occupying 52.8%; 466 females, occupying 47.2%. In respect with grade level, there were 482 grade-5 students, occupying 48.8%; 505 grade-6 students, occupying 51.2%. Based on an analysis of data using structural equation modeling (SEM), we reached the following conclusions: 1 There was a significant positive correlation between father-child and mother-child interactions; 2. There was a significant positive correlation between parent-child interaction, gratitude, and prosocial behavior; 3. Gratitude mediated the relationship between parent-child interaction and prosocial behavior.