English-learning infants attend to lexical stress when learning new words. Attention to lexical stress might be beneficial for word learning by providing an indication of the grammatical class of that word. English disyllabic nouns commonly have trochaic (strong–weak) stress, whereas English disyllabic verbs commonly have iambic (weak–strong) stress. We explored whether 17-month-old infants use word stress to resolve an ambiguous labeling event where objects and actions are equally plausible referents. Infants were habituated to 2 words paired with 2 objects, with each object performing a distinct path action. They were subsequently tested on (a) a change in object but not path action or (b) a change in path action but not the object. When infants were taught verb-friendly iambic labels, their looking times increased both when the action switched and when the object switched. Infants who were taught noun-friendly trochaic labels demonstrated an increase in looking time only when the object switched. These results demonstrate that in ambiguous labeling events infants map iambic labels to both actions and objects, and trochaic labels to the objects but not to the actions, suggesting a bias for words with trochaic stress to refer to objects. Seventeen-month-old infants can use trochaic lexical stress to guide their word learning in ambiguous situations, but iambic stress cues may not preferentially guide infants’ mappings of actions or objects.