In collaborative decision-making, partners compare reasons behind conflicting proposals through meta-talk. We investigated UK-based preschoolers' (mixed socioeconomic status) use of meta-talk (Data collection: 2018-2020). In Study 1, 5- and 7-year-old peer dyads (N = 128, 61 girls) heard conflicting claims about an animal from two informants. One prefaced her claim with "I know"; the other with "I think". Dyads identified the more reliable informant through meta-talk ("She said she knows"). In Study 2, 3- and 5-year-olds (N = 64, 34 girls) searched for a toy with an adult partner making incorrect proposals. Children refuted this through reporting what they had witnessed (It cannot be there because "I saw it move", "she moved it"). In preschool period, children start using meta-talk to make rational collaborative decisions.