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Here, we report a thickness-dependent ferromagnetism in epitaxially grown Cr₂Te₃ thin films and investigate the evolution of the underlying electronic structure by synergistic angle-resolved photoemission spectroscopy, scanning tunneling microscopy, x-ray absorption spectroscopy, and first-principle calculations. A conspicuous ferromagnetic transition from Stoner to Heisenberg-type is directly observed in the atomically thin limit, indicating that dimensionality is a powerful tuning knob to manipulate the novel properties of 2D magnetism. Our results establish atomically thin Cr₂Te₃ as an excellent platform to explore the dual nature of localized and itinerant ferromagnetism in 2D magnets.