Green transit-oriented development (TOD) is an evolution of the TOD theory, influenced by sustainable development and green urbanism. This advancement expands the environmental and ecological dimensions of conventional TOD. However, relevant research has only just started, particularly in combination with high-density cities in Asia. This study measures the built environment of Green TOD and identifies the key factors and characteristics of the Green TOD built environment. An evaluation method for the Green TOD built environment is developed on the basis of the 5D (density, diversity, design, destination, and distance) built environment framework and combined with green urbanism theories. Data from 23 rail station areas in Singapore were collected and analyzed using factor and cluster analysis. Five factors, namely, neighborhood spatial form factor, facility completeness factor, open space factor, high-density mixed land-use factor, and walking amenity factor, are extracted. Twentythree station areas are classified into five clusters. The characteristics and optimization strategies of each cluster are analyzed on the basis of the statistical and graphical analyses. This research displays the characteristics and typology of the Green TOD built environment in an empirical way and offers a foundation for further research in diverse urban contexts.