Source representations play a role both in the formation of individual beliefs as well as in the social transmission of such beliefs. Both of these functions suggest that source information should be particularly useful in the context of interpersonal disagreement. Three experiments with an identical design (one original study and two replications) with 3-to 4-year-oldchildren (N = 100) assessed whether children's source memory performance would improve in the face of disagreement and whether such an effect interacts with different types of sources (first-vs. secondhand). In a 2 x 2 repeated-measures design, children found out about the contents of a container either by looking inside or being told (IV1). Then they were questioned about the contents of the container by an interlocutor puppet who either agreed or disagreed with their answer (IV2). We measured children's source memory performance in response to a free recall question (DV1) followed by a forced-choice question (DV2). Four-year-olds (but not three-year-olds) performed better in response to the free recall source memory question (but not the forced-choice question) when their interlocutor had disagreed with them compared to when it had agreed with them. Children were also better at recalling 'having been told' than 'having seen'. These results demonstrate that by four years of age, source memory capacities are sensitive to the communicative context of assertions and serve social functions.