This study examined the contribution of working memory (WM) above and beyond other domain general (e.g., processing speed; PS) and domain specific abilities (e.g., Approximate Number System; ANS) for mathematical performance in low achieving (LA) preschool children. Pre-schoolers aged 3 to 5 years (N = 139) were included in the study. Children performing below the 35th percentile on a Test of Early Mathematical Abilities (TEMA-3) were considered LA and at potential risk for later mathematical learning difficulties (MLD). First, the relationships between measures of simple and central executive visuospatial and verbal WM tasks (forward, backward, and dual processing tasks), ANS, PS abilities and early mathematical abilities were explored. Then, the contribution of these measures in predicting low mathematical performance was examined in several stepwise logistic regressions. The results showed that all measures were significantly correlated, and that ANS alone explained only a smaller amount of variance in low maths achievement. Surprisingly, PS did not contribute to prediction of low maths achievement and when visuo-spatial and verbal WM measures were added to the analyses they alone explained variance to a large degree. We concluded that central executive WM and particularly backward processing ability seems to play an important role in the development of mathematical abilities in LA preschool children. Results were discussed in relation to research on WM, executive functions (EF), and early mathematical development. Conclusions for early screening and intervention in preschool were also drawn.