The White-necked Jacobin is a large hummingbird with a white neck band and a fan-shaped tail. It visits tropical lowland forest edges, clearings, and gardens, feeding at different heights.
Males have a blue head, green upperparts, a white neck band, and a white belly; they may fan the tail. Females vary from male-like birds to birds with spotted underparts and mostly green tails.
It uses forest edges, nearby clearings, and flower-rich gardens, feeding at different levels, often in the canopy. It may hover with its tail spread.
An extinction-risk assessment has not been added yet.