To help infer the meanings of novel words, children frequently capitalize on their current linguistic knowledge to constrain the hypothesis space. Children's syntactic knowledge of function words has been shown to be especially useful in helping to infer the meanings of novel words, with most previous research focusing on how children use preceding determiners and pronouns/auxiliary to infer whether a novel word refers to an entity or an action, respectively. In the current visual world experiment, we examined whether 28- to 32-month-olds could exploit their lexical semantic knowledge of an additional class of function words--prepositions--to learn novel nouns. During the experiment, children were tested on their ability to use the prepositions "in," "on," "under," and "next" to to identify novel creatures displayed on a screen (e.g., "The wug is on the table"), as well as their ability to later identify the creature without accompanying prepositions (e.g., "Look at the wug"). Children overall demonstrated understanding of all the prepositions but "next to" and were able to use their knowledge of prepositions to learn the associations between novel words and their intended referents, as shown by greater-than chance looks to the target referent when no prepositional phrase was provided.