Recent research demonstrated that although twenty-four month-old infants do well on the initial pairing of a novel word and novel object in fast-mapping tasks, they are unable to retain the mapping after a five-minute break. The current study examines the role of familiarity with the objects and words on children’s retention in fast-mapping tasks. Twenty-four month-old infants were familiarized with either a series of novel objects or a series of novel names prior to the referent selection portion of a fast-mapping task. Infants retained the novel mapping after a delay when familiarized with the novel objects, but did not demonstrate retention when familiarized with the novel words. The results suggest familiarity with the object or word-form lead to differential encoding of the name-object link and altered subsequent word learning.