In languages with evidential marking, utterances consist of an informational content and a specification of the mode of access to that information. In this first longitudinal study investigating the acquisition of the Turkish evidential marker "-mIs" in naturalistic child-caregiver interactions, we examined six children between 8 and 36 months of age. We charted individual differences in child and caregiver speech over time by conducting growth curve analyses. Children followed a similar course of acquisition in terms of the proportion of the marker in overall speech. However, children exhibited differences with respect to the order of emergence of different evidential functions (e.g., inference, hearsay), where each child showed a unique pattern irrespective of the frequency in caregiver input. Nonfactual use of the marker was very frequent in child and caregiver speech, where high-SES caregivers mostly produced the marker during story-telling and pretend play, and low-SES caregivers for regulating the child's behavior.