Child maltreatment is characterized by a harmful relational environment which can have negative cascading consequences for the child’s development. Relationship-based interventions may improve maltreated children’s functioning by addressing key aspects of the parent-child relationship at various stages of development. The objective of the current study was to perform a systematic review on relationship-based interventions for maltreated children and a meta-analysis on the impact of these interventions on observed parent-child relational behavior. Data collection consisted of a comprehensive literature search in six databases and contacting experts in the field and hand searching relevant publications. In total, 5,802 abstracts were screened, of which 81 relevant publications were identified, representing 4,526 participants. The meta-analysis found large improvements in observed parent interactive behavior (g = 0.888), smaller improvements in child attachment (g = 0.403) and child interactive behavior (g = 0.274). The effect on parent interactive behavior was larger in interventions addressing middle childhood. Risk of bias assessments showed that a large number of studies suffer from poor reporting, which limits the conclusions of the findings. Future research should examine parent-child relationship behavior across multiple developmental stages, as well as the impact of developmentally appropriate intervention elements on maltreated children.