Aims and Objectives/Purpose/Research Questions: Second language researchers have focused increasingly in recent years on “heritage language learners,” or adult learners who wish to learn, relearn, or improve their linguistic proficiency in a family language they spoke while growing up. The present study examines this domain with a particular focus on Arabic. Design/Methodology/Approach: We present in this paper a “scoping review” that systematically examines the theoretical approaches, methods, contexts, instruments, and linguistic foci found in empirical research on Arabic heritage language learning and learners. Following a comprehensive search, 34 empirical studies (27 journal articles and seven dissertations/theses) were identified that met our criteria. Data and Analysis: Each study was coded for the samples, designs, theoretical approaches, data collection instruments, and a number of other substantive and methodological features and practices. Frequencies and percentages of study features were then calculated. Findings/Conclusions: Among other results, the study revealed a variety of approaches to defining heritage learners/learning. Although studies in this domain most often employed cross-sectional designs and interviews to collect data, a variety of theoretical approaches both socially and cognitively oriented can be found. Originality: This study presents the first attempt to apply synthetic research techniques to the growing body of research on heritage language learning/learners. Significance/Implications: Our results describe this growing domain, identifying current trends and potentially fruitful directions for future research.