Two studies addressed whether children consider speakers' knowledge states when establishing initial word-referent links. In Study 1, forty-eight 3- and 4-year-olds were taught two novel words by a speaker who expressed either knowledge or ignorance about the words' referents. Children showed better word learning when the speaker was knowledgeable. In Study 2, forty-eight 3- and 4-year-olds were taught two novel words by a speaker who expressed uncertainty about their referents. Whether the uncertainty truly reflected ignorance, however, differed across conditions. In one condition, the speaker said he made the object himself and thus, he was knowledgeable. In the other condition, the speaker stated that the object was made by a friend and thus, expressed ignorance about it. Four-year-olds learned better in the speaker-made than in the friend-made condition; 3-year-olds, however, showed relatively poor learning in both conditions. These findings suggest that theory-of-mind developments impact word learning.