The research synthesis presented here reviewed the currently available evidence on the effectiveness of parent-implemented interventions and family-centered service delivery approaches in early intervention, early childhood special education, and kindergarten through grade three (EI/ECSE [early childhood special education]/K-3). The search for appropriate research literature spanned from 2005 to 2018 and resulted in a total of fifteen studies that met the inclusion criteria. Taken together, the outcomes of this research synthesis provide support for the effectiveness of parent-implemented interventions for children with or at risk for developmental delays/disabilities. Also, there is evidence to support the efforts that have been made to train EI/ECSE professionals in adopting these practices in their profession. However, no evidence was gained to clarify if the implemented interventions were aimed to help the child and the family with Individualized Family Service Plan (IFSP) or Individualized Educational Plan's (IEP) goals' attainment. Discussion of the findings along with implications for future research and practice are presented.