This article explores the relationship between the writing proficiency of heritage speakers of Mandarin Chinese, Korean, and Spanish and their context of acquisition, educational experiences, and language practices. Biographical data and proficiency ratings obtained with the ACTFL Writing Proficiency Test were collected for 187 adult heritage speakers. These data are analyzed in order to shed light on connections between the writing proficiency of heritage speakers of these three languages and their language experiences, which have implications for placement and pedagogy in the postsecondary setting. The results of the analysis are then deployed in a series of recommendations to support the development of writing proficiency in the classroom. The authors advocate a proficiency-oriented approach to the teaching of heritage language that leverages the learners' linguistic resources.