As of 2024, nearly three decades have passed since Bonny Norton introduced the investment model. This bibliometric review analyses research on this model using metadata from 424 publications indexed in the Web of Science database. Employing bibliometric techniques, the study identifies and visually presents significant sources, countries, institutions, and leading authors. It also examines influential works through h-classics publications. The findings reveal (a) a consistent increase in research related to the investment model over the past decade; (b) a broad range of dissemination sources across disciplines like linguistics, sociolinguistics, education, psychology, cultural studies, and sociology; (c) the prominent role of Norton in research and collaborations; and (d) a strong focus on language learners and teachers' identity construction and agency, multilingual education, language learning and teaching investment, and cultural and ideological factors, with significant attention to technology and power dynamics. Additionally, the review of the h-classics suggests future research directions, including the (dis)investments of international students, immigrants, and asylum seekers in learning languages other than English (LOTEs), investments in teaching LOTEs in Asia and exploration of language teacher identities and their challenges related to race, sexual orientation, and legitimacy. This research is essential for advancing inclusive language education in multilingual contexts.