Located where the biotas of the Indian Subcontinent and the Indochinese Peninsula meet, and in the transition between subtropical and tropical regions of Asia, the Mizoram–Manipur–Kachin rain forests are home to great biodiversity.

Rainfall comes mostly from the monsoon winds from the Bay of Bengal, and parts of the ecoregion can receive up to 2,000 millimetres (79 in) of rain per year.

Trees of other families include Swintonia floribunda, Eugenia grandis, Xylia xylocarpa, Gmelina arborea, Bombax insignis, Bombax ceiba, Albizia procera, Citrus macroptera, Cinnamomum cassia, Durio zibethinus, Artocarpus heterophyllus, Ficus benghalensis, Gnetum gnemon, Mangifera indica, Toona ciliata, Toona sinensis, Cocos nucifera, Tetrameles nudiflora, Ginkgo biloba, Prunus serrulata, Camphora officinarum, Pinus roxburghii, Pinus hwangshanensis, Juniperus tibetica, Olea europaea subsp.

cuspidata, Taxus sumatrana, Juglans regia, Alnus nepalensis, Betula alnoides, Betula utilis, Larix griffithii, Picea brachytyla, Cathaya argyrophylla, Taiwania cryptomerioides, Cyathea spinulosa, Sassafras tzumu, Davidia involucrata, Metasequoia glyptostroboides, Glyptostrobus pensilis, Castanea mollissima, Quercus myrsinifolia, Quercus acuta, Quercus glauca, Machilus thunbergii, Tetracentron, Tsuga dumosa, Ulmus lanceifolia, Tectona grandis, Terminalia elliptica, Terminalia bellirica, Larix gmelinii, Larix sibirica, Larix × czekanowskii, Betula dahurica, Betula pendula, Pinus koraiensis, Pinus sibirica, Pinus sylvestris, Picea obovata, Abies sibirica, Quercus acutissima, Quercus mongolica, Prunus padus, Tilia amurensis, Salix babylonica, Acer palmatum, Populus tremula, Ulmus davidiana, Ulmus pumila, Pinus pumila, Haloxylon ammodendron, Elaeagnus angustifolia, Tamarix ramosissima, Prunus sibirica, and Castanopsis spp.

The ecoregion is home to several endangered and threatened mammal species, including the tiger (Panthera tigris), clouded leopard (Pardofelis nebulosa), Asian elephant (Elephas maximus), Eld's deer (Cervus eldii), gaur (Bos gaurus), Himalayan goral (Nemorhaedus goral), red panda (Ailurus fulgens), smooth-coated otter (Lutrogale perspicillata), Indian civet (Viverra zibetha), back-striped weasel (Mustela strigidorsa), Assamese macaque (Macaca assamensis), bear macaque (Macaca arctoides), southern pig-tailed macaque (Macaca nemestrina), capped leaf monkey (Semnopithecus pileatus), and hoolock gibbon (Hylobates hoolock).