In a randomised controlled trial, we investigated if adaptive, computerised working memory training using Cogmed was associated with greater neural changes compared with a placebo training program. Participants were a population-based cohort of 91 school-age children born <28 weeks’ gestation or <1000 g birthweight. Children had structural, diffusion and task-based functional MRI before and two weeks following five weeks of Cogmed or placebo. There was little evidence for larger changes in cortical morphometry, white matter microstructure, or brain functional activity following Cogmed compared with placebo. In our study, Cogmed did not benefit brain structure or function in preterm-born children.