The relationship between high dietary intakes of sugar (sucrose) and dental caries is well established. Processed sugars and starches have been associated with greater dental caries experience in retrospective studies. The aim of this systematic review was to determine the relationship between the consumption of processed sugar- and starch-containing foods, the frequency of consumption of these foods, and dental caries. Prospective studies were identified in databases searched from 1970 to July 2020, and relevant retrieved papers that examined associations between the consumption of sugar- and starch-containing foods by human participants and dental caries were eligible for inclusion. Five cohort studies were identified for inclusion, all of which evaluated caries risk in young children or pre-adolescents. The between-meal consumption of processed sugar- and starch-containing foods was consistently found to be associated with greater caries experience. There were mixed findings on total consumption of processed sugar- and starch-containing foods, owing to a range of confounding factors, including the simultaneous consumption of caries-protective foods at mealtimes. Although there is a paucity of research of the dietary effects of frequent consumption of processed sugar- and starch-containing foods on dental caries, there is some evidence of plausible associations between this dietary behaviour and dental caries. Future research should investigate the effectiveness of interventions to change the dietary behaviour of high-frequency consumption of processed sugar- and starch-containing foods to decrease the risk of dental caries.