Chestnuts (Castanea spp.) are ecologically and economically important forest and fruit trees. They are cultivated for their nutritious nuts. To select varieties to be cultivated in chestnut orchards, their phenology needs to be considered. In this work, we adapt the international BBCH system to chestnuts by building on an existing phenological scale used in some European countries for these species. The proposed BBCH scale uses eight of the ten principal growth stages for fruit trees and secondary growth stages that are specific to chestnut trees. We tested it by monitoring chestnut trees phenology during three growing seasons, illustrating its suitability for high-throughput phenotyping studies. Overall, the approach used, despite its inherent limitations, is straightforward, accessible and flexible, allowing particularly precise description of the complex flowering phenology of these trees.