The purpose of this study was to examine the effects of mental abacus training on children’s working memory. To accomplish this, the role played by the visuo-spatial sketchpad and phonological loop with regard to the working memory task in three experiments, and three distraction tasks were manipulated to investigate it. The results of experiments 1–3 suggest that training to perform mental arithmetic calculations and digit span enhances participants’ ability to retain visuo-spatial and phonological loop information. Additionally, children who had not received mental abacus training depended on the phonological loop to retain numerical information. We speculate that these children may execute mental calculations using their visuo-spatial sketchpad to form mental imagery. These findings demonstrate that mental abacus training may improve basic cognitive capacities and possess utility for learning and education.