The Himalayan arc has wide elevational and precipitation gradients that lack parallels elsewhere. This wide gradient encompasses a variety of ecosystems from tropical to alpine, which support a high degree of floral/faunal diversity that makes the Himalayas home to two global biodiversity hotspots. Despite the high diversity of endemic trees, the Himalayas is one of the underexplored mountain forest ecosystems in terms of seed ecology that demands much more attention and offers an opportunity to study how seed traits modulate tree assembly along altitudinal and longitudinal gradients of the Himalayas. This chapter aimed to collate fruit/seed traits of Himalayan trees from published literature and to unravel how much seed ecological traits differ with wet-dry season and along large macroclimatic gradients of the Himalayas. The results revealed that 23% of the tree species fully and 57% partially synchronised seed dispersal and germination with monsoon. Desiccation-sensitive, non-dormant, and wet-season dispersed seeds germinate primarily in the monsoon, whereas desiccation-tolerant, dormant, and dry-season dispersed seeds germinate within or outside the monsoon season. The percentage of fleshy-fruited, zoochorous, desiccation-sensitive, non-dormant seeded species was higher in the eastern Himalayas, while the percentage of dry-fruited, anemochorous, desiccation-tolerant, dormant seeded species was higher in the western Himalayas; however, these differences were not significant. Contrary to the longitudinal trends, there were inconsistencies in the altitudinal trends in seed traits of the species from the lower to the higher Himalayas. Seed dormancy increases from monsoon-synchronised to -desynchronised species, and approximately 75% of species in intermediate/dry habitats produce dormant seeds. Deciduous and evergreen species with long-leaf lifespans produced more anemochorous, desiccation-tolerant, and dormant seeds than those evergreen species with short-leaf lifespans, which may drive their desynchronisation or synchronisation with monsoon, respectively. The study concluded a weak/non-significant longitudinal and altitudinal trend in tested seed ecological traits and that the microscale level variability of heterogenous landforms in the Himalayan arc may have masked seed trait variation prevalent at the macroscale level. However, even identifying weak trends in the seed ecological traits of tree species along the Himalayan gradient will help us better understand their regeneration ecology and vulnerability to climate. Finally, this chapter also proposed a few future research agendas requiring urgent attention to better understand the Himalayan forest ecosystem.