This article investigates the early emergence of reason-giving. Toddlers are sensitive to disagreements, and they can track several kinds of informational access, such as visual perception. We investigated whether young children use these skills (a) when assessing whether providing reasons is needed and (b) when selecting appropriate behaviors to support their claims. An experimenter disagreed with 2- to 4-year-old children (N = 71) about the location of a toy placed in 1 of 4 boxes. In the fully transparent condition, the boxes were transparent, and the toy was visible to the experimenter and to the participant. In the window condition, the boxes were partially opaque, and the toy was initially hidden from the experimenter but visible to the participant through a transparent window. In this condition, toddlers could make the toy visible to the experimenter by rotating the baited box. Participants in the window condition were more likely to rotate the baited box than those in the transparent condition. Thus, children were more likely to rotate the box when this action was an efficient way of supporting their claims by revealing new and relevant information to the experimenter. These results demonstrate the presence of precursors of crucial skills required for reason-giving and reveal that from 2 years of age, children do not use fixed persuasion strategies. Instead, they select relevant evidence when attempting to influence others.