Communication between parents and their children represents an important factor of family socialization. Nevertheless, little is known about why parents communicate in different ways and how these qualitative differences in parent-child communication may affect the child. Building on self-determination theory, the present study focuses on motivational antecedents of need-supportive communication as a function of parental child-related beliefs (i.e.,long-term goals that parents have set for their children's future, and parental child-related behavior expectations in terms of parental dissatisfaction or satisfaction with child behavior). Moreover, the effect of perceived need-supportive communication on children's prosocial behavior and (externalizing and internalizing) behavioral difficulties will be addressed. Three waves of data from 1125 mothers and adolescents aged between 10 and 17 years were analyzed using growth-curve modeling. We found linearly increasing trajectories in extrinsic parental goals for children and dissatisfaction with child behavior, and decreasing trajectories of need-supportive communication. Individual differences do not vary significantly over time. In addition, holding extrinsic parental goals for children positively predicts parents' dissatisfaction with their child's behavior and negatively predicts need-supportive communication. Parents' dissatisfaction with their child's behavior also contributes to decreasing need-supportive communication. As expected, need-supportive communication predicts prosocial behavior and externalizing behavioral difficulties. When need-supportive communication decreases over time, both externalizing and internalizing behavioral difficulties increase. Furthermore, the effect of mothers beliefs on adolescents socioemotional development was mediated through perceived mother's communication quality. These results suggest that parental child-related beliefs are important motivational antecedents of parent-child communication that may prevent behavioral difficulties.