Complex numerals (e.g., four hundred) have a multiplicative structure (four hundred = 4 x 100). This paper investigates whether children are sensitive to the meaning of the multiplicative structure. We designed a novel word learning paradigm and taught 4- to 6-year-old children the meaning of a novel numeral phrase (e.g., ‘one gobi houses’ to mean a group of three houses). We then asked whether they could generalize it to a novel context (e.g., ‘two gobi butterflies’ to mean two groups of three). Experiment 1 showed that only English-speaking children who received multiplier syntax training were able to generalize. Experiment 2 extended findings from Experiment 1 to Cantonese-speaking children and found that they could also generalize a novel multiplier to novel contexts. These results suggest that children as young as 4 can create a mapping between the structure of complex numerals and a multiplicative meaning.