Disparities in language development emerge in the first year of life and increase with age; consequently, infancy and toddlerhood are key periods whereby early language outcomes may be optimised via prevention and early intervention programs. As yet, the efficacy of programs promoting early language in the first three years of life remains unknown. This chapter provides the reader with findings from a systematic review of interventions aimed at improving child language outcomes for 0–3 year olds. Using a narrative synthesis, we examine and describe the evidence for effective language interventions across the preventive intervention spectrum (universal, selective, indicated/targeted). Specifically, we explore what works for who and under what circumstances. This review provides important insights about early language interventions, including factors contributing to positive outcomes. Findings also suggest how early interventions may be tailored to foster language outcomes for different groups of children (i.e. targeting children at-risk based on low socio-economic status or those with identified language difficulties). This review also highlights the need for further evaluation of promising interventions when applied to the broader population.