Dopamine (DA) is implicated in working memory (WM) functioning. Variations in the DA transporter (DAT1) gene (SLC6A3) regulate DA availability in striatum. Compared to DAT1 9/10-repeat carriers, homozygosity of the DAT1 10-repeat allele has been related to less active dopaminergic pathways. A group of younger adults received 4 weeks of computerized adaptive training on several WM tasks. All participants improved their performance as a function of training. However, DAT1 9/10-repeat carriers showed larger training-related gains than DAT1 10-repeat carriers in visuospatial WM. By contrast, the two groups were indistinguishable in baseline WM performance as well as in a variety of tasks assessing different cognitive abilities. This pattern of results provides novel evidence that WM plasticity is a more sensitive indicator of DAT1 gene-related cognitive differences than single-assessment performance scores.