Aquifoliaceae Ilex cookii is an evergreen shrub 3 meters tall with light brown bark and prominent lenticels. The upper surface is dark shiny green and the underside is pale green with microscopic black dots. Flowers are dioecious, solitary or fascicled and axillary.
Petals are white and about as large as the sepals.
The species was collected for the first time in 1926 by Gleason and Cook in what is considered one of the first botanical explorations of the Cordillera Mountains. It was published as a new species by Britton and Wilson in their addendum to the flora of Puerto Rico. It is named after the collector Melville Cook. Date 13 MAR 96 holotype of the species is maintained at the New York Botanical Garden. The species has this status wherever found including the Commonwealth of Puerto Rico.