Forest aboveground biomass serves as an important indicator of carbon resources and carbon sequestration in terrestrial systems, and its accurate estimation is crucial for carbon evaluation. Allometric equations are among the most commonly used approaches, but the frequent misuse of locally developed models at a different scale has often led to biased results. Despite many attempts to construct generally applicable allometric equations, two crucial factors of plant functional types and origins have rarely been incorporated into the allometric equation models. In this study, the effectiveness of incorporating both plant functional types and origins into generic models was investigated using a newly compiled data set in Japan. The results showed that incorporating both plant functional type and origin into models significantly improved model performance. The results of this study suggest that the inclusion of both plant functional type and plant origin in generic allometric equations is essential, and highlight the possibilities of including both plant functional types and origins in models for accurate estimation of forest AGB in Japan.