To perform an overview of systematic reviews and more recent randomized controlled trials (RCTs) on early motor interventions in infants aged 0 to 3 years with or at risk of cerebral palsy to inform current clinical and research efforts and provide a benchmark to assess future interventions ideally initiated within the first 6 months. Standardized searches of the PubMed, Embase, Scopus, and Web of Science databases were conducted for systematic reviews (2009-2020) and RCTs (2015-2020). From 840 unique records, 31 full texts were reviewed, yielding three systematic reviews encompassing 46 studies, 16 with comparison groups, and six additional RCTs that met the criteria. Two enrichment- and activity-based approaches had medium effect sizes on motor development, only one with low risk of bias; two others had large task-specific effect sizes but some bias concerns; and three enriched environment studies with some bias concerns had medium effect sizes on cognitive development. Most had small or no effect sizes, bias concerns, and uncertain diagnostic determinations. Data synthesis revealed limited data quantity and quality, and suggest, although not yet confirmed, greater benefit from early versus later intervention. Research efforts with greater early diagnostic precision and earlier intervention are accelerating, which may transform future outcomes and practices. What this paper adds For over 50% of trials within the reviews, the intervention was compared to standard care with only two showing efficacy. Similar to results in older children, constraint-induced movement therapy (CIMT) emerged as efficacious with high effect sizes. CIMT was not superior to similarly intense bimanual training or occupational therapy. Goals-Activity-Motor Enrichment intervention initiated before 5 months of age was superior to equally intense standard care. Several other enriched environment strategies promoted cognitive and/or motor development.