This case study examines caregiver language in sixteenth- and seventeenth-century letters. It addresses the general issue of how parents and other caregivers talked about and communicated with children and adolescents in their personal correspondence, and, more specifically, to what extent it is possible to reconstruct patterns of child-directed language using personal letters as data. The study analyses the patterns of discourse and linguistic models that Lady Katherine Paston transmitted in her letters to her teenage son. Her usage is also compared with interadult communication. The results obtained indicate that the caregiver language of the past can be characterized at various levels: speech activity and politeness phenomena, lexical content, and even ongoing processes of language change.