Associations between diet and cardiometabolic outcomes are often based on a single measurement of diet in adulthood. Dietary exposures in childhood are thought to influence cardiometabolic disease development and individuals' diets can change over time, therefore dietary exposure in childhood and over long periods are both important to consider. This scoping review aimed to identify and characterise the literature on associations between diet measured in both childhood and adulthood and cardiometabolic outcomes. Seven databases were searched; eligible evidence sources were original analyses published as a journal article in English. Exposures included measures of dietary intake, diet quality and eating behaviours measured in both childhood and adulthood with at least five years between first and last measurements. Cardiometabolic outcomes included measures of anthropometry, biochemistry, vascular structure/function and disease states/scores. We identified 37 eligible articles from nine cohort studies. Dietary exposures were measured between two and eight times and most often assessed by food frequency questionnaire or diet history. The dietary exposures most frequently examined were protein, fat, carbohydrate, fruit, vegetables, sugar-sweetened beverages and breakfast. Cardiometabolic outcomes were predominantly based on risk markers. Authors utilised a variety of analytical approaches to transform and analyse repeated measures of diet, providing insights relevant to different lifespan nutrition concepts. The literature on associations between diet in childhood and adulthood and cardiometabolic outcomes is limited, but such studies have great potential to extend our knowledge in ways only possible with repeated measures of diet over time. Further research is needed to develop the evidence base for diet-disease relationships from a life course perspective, accounting for diet in both childhood and adulthood. © 2021 The British Dietetic Association Ltd.