Interventions to enhance cognitive and executive function performance are essential for the child's performance in current and future occupations. Occupational therapy practitioners are critical members of early intervention, education, and healthcare teams. Practitioners are distinctly qualified to address cognitive functioning within the context of occupational performance by providing evidence-based interventions to children and their families as well as training caregivers and teams to enhance cognitive and executive functioning (EF) performance. The purpose of this review was to update the previous systematic review on this topic. The focused question guiding the selection of research studies was: "What is the evidence for the effectiveness for interventions within the scope of occupational therapy practice to promote cognitive development and prevent further delay for children 0-5 and their families?" Due to the breadth of the review, the results were divided into two articles. This article (Part 1) focuses on cognitive interventions for children birth to 5 years with known conditions while Part 2, also in this issue, will address findings on interventions for children at risk due to environmental factors and promoting cognitive development for children birth to 5 years. [For Part 2, see EJ1333259.]