Tropical rainforests have strongly influenced Earth systems throughout their evolutionary history. Plant taxa found in the Fotan Group of Fujian Province indicate that an Asian tropical rainforest prevailed in southeastern China during the Miocene. Abundant insect-bearing ambers co-occur with diagnostic plant fossils in outcrop. Fotan Group fossils demonstrate that highly diverse tropical ecosystems existed during the early Neogene in southeastern China. This study reports a robust Ar-40/Ar-39 age of 14.7 +/- 0.4 Ma for the Fotan fossils. This age constrains interpretations of 1) when tropical rainforest ecosystems developed in China, 2) whether the Fotan flora temporally overlapped with the Asian tropical forest in India, and 3) whether the Middle Miocene Climatic Optimum triggered expansion of tropical rainforests in Asia. A precise age for Fotan units provides important constraints on the biogeographic history of the field area and paleographic models linking Asian and Indian biota.