ABSTRACT: The paucity of data on colonization of benthic invertebrates in the deep sea can severely inhibit our ability to predict the potential for recovery of these vulnerable ecosystems from anthropogenic disturbances, such as deep sea mining and trawling. In this study, we measured abundance and family richness of benthic invertebrate colonists on 2 types of substrates with the same planar area, but different levels of structural complexity, at 3 locations (655, 662 and 883 m depth) in the Middle Canyon of the Northeast Channel Coral Conservation Area, NW Atlantic, over 4 yr. The complex substrate allowed colonization in the third dimension, while the simpler substrate allowed colonization in only 2 dimensions. Anthozoan and bivalve colonists were present at a higher frequency on simple substrates, and maxillopods, nematodes, gastropods and ostracods on complex ones. Abundance of colonists varied among locations, but not consistently for all taxa and substrate types. Family richness of the colonizing assemblages was greater on complex than on simple substrates and also varied among locations in the canyon. Colonization on simple substrates was low and similar to those few values previously recorded in deep-sea, non-chemosynthetic habitats. Colonization on complex substrates was higher, in some cases by an order of magnitude, and similar to other studies that have used complex substrates. Overall, the low rates of colonization in the deep sea indicate the vulnerability of these ecosystems to anthropogenic disturbances.