Children with mild intellectual disabilities (MID) appear to have particular problems in understanding the numerical meaning of Arabic digits. Therefore, we developed and evaluated a numerical domino game that specifically targeted the association between these digits and the numerical magnitudes they represent. Participants were 30 children with MID (M?=?8.36?years), randomly assigned to either the numerical domino game or to a control color domino game. Findings revealed that both groups of children improved on a nonsymbolic comparison and arithmetic task. Most importantly, only children who played the numerical domino game became significantly faster from pretest to posttest on a symbolic comparison task. These findings suggest that numerical magnitude processing can be successfully trained in children with MID.