Informed by the Innocenti framework, this rapid review of systematic reviews (n = 60) and sentinel grey literature (n = 27) synthesises the evidence of what works to improve nutrition and food sustainability across the first 2000 days. Most systematic reviews focused on interventions targeting the behaviour of parents and caregivers (n = 49), with fewer reviews focusing on the personal (n = 7) and external (n = 4) food environments. No reviews focused on food supply-chain activities. Most reviews were rated as critically low (n = 28, 47%) or low (n = 21, 35%) quality using AMSTAR 2. Evidence supports the effectiveness of multi-component breastfeeding interventions, interventions delivered in home and child-care settings, particularly when involving parents, interactive skill building and repeated exposure to vegetables. Food vouchers and access to local farmers markets and community gardens have potential for improving access and availability to healthier foods, while evidence supports interventions improving the external food environment, including fiscal strategies such as the SSB tax, restrictions on marketing and advertising of discretionary products and improved food labelling. Overall, this review highlights the importance of action across a range of settings and sectors at the international, national and local levels to improve young children’s diets.