Grevillea caleyi is an open, spreading shrub that typically grows 1–4 m (3 ft 3 in – 13 ft 1 in) tall and up to 4 m (13 ft) wide. It has deeply divided leaves that are comparatively large in size, 70–180 mm (2.8–7.1 in) long and 30–75 mm (1.2–3.0 in) wide with 19 to 36 linear to lance-shaped lobes, with the narrower end towards the base. The lobes are 15–35 mm (0.59–1.38 in) long, 2–6 mm (0.079–0.236 in) wide with the edges turned downwards, and hairy on the lower surface. The flowers are arranged in toothbrush-like groups on a rachis 40–80 mm (1.6–3.1 in) long, and are fawn with a maroon to red style with a green tip. The pistil is 25–28 mm (0.98–1.10 in) long and the style is glabrous. Flowering is sporadic and occurs throughout the year, mostly from August to December. Fruit is a woolly hairy follicle 17–21 mm (0.67–0.83 in) long with reddish brown stripes or blotches.^[3][4][5][6]

Grevillea caleyi was first formally described in 1830 by Robert Brown in Supplementum primum prodromi florae Novae Hollandiae from specimens collected in 1805, near Port Jackson by George Caley.^[7][8] The species has the common name Caley's grevillea.^[9]

Caley's grevillea is restricted to an 8km² area in the Terrey Hills-Belrose area north of Sydney. It grows on iron-rich laterite sandstone soils on ridgetops between elevations of 170-240m above sea level in open forest.^{[1][4][10][11]}

It occurs in the endangered Duffys Forest ecological community. The structure of this ecological community is an open forest with a tree canopy of species such as Corymbia gummifera, Eucalyptus sieberi and Eucalyptus haemastoma, Banksia serrata and Xylomelum pyriforme.

Other species commonly associated with G. caleyi include other shrubs such as Acacia myrtifolia, Banksia spinulosa, Conospermum longifolium, Grevillea buxifolia, Hakea dactyloides, Lambertia formosa, Pimelea linifolia and Telopea speciosissima and herbaceous plants including Anisopogon avenaceus, Dampiera stricta, Lomandra glauca, Lomandra obliqua and Pteridium esculentum.^[11]

Grevillea caleyi is killed by fire, and relies entirely on seed that is stored in the soil for regeneration. It does not form a lignotuber and does not propagate by suckering. Due to fecundity and seed dispersal being low and seed predation being high, it is estimated that it takes 8-12 years for a sufficient seedbank to develop to be able to replace a population. Generally, seedlings are not able to produce flowers or seeds before 2-5 years of age.^[10]

This species is pollinated by birds. Through casual observations, the likely common pollinators for this species include honeyeaters such as New Holland, white-eared and white cheeked, silvereyes, Little wattlebirds and Eastern spinebills. It is thought this species may be self-compatible as well.^[10][11]

Caley's grevillea is listed as Critically Endangered on the IUCN Red List of Threatened Species, under the Australian Government Environment Protection and Biodiversity Conservation Act 1999 and the New South Wales Government Biodiversity Conservation Act 2016. The extent of occurrence (EOO) of this species is less than 100km² and its area of occupancy is less than 10km². The population is severely fragmented and its population and quality of its habitat is are in continuous decline as a result of habitat loss from development.

It became locally extinct in one area in 2011 and a quantitive analysis by the Threatened Species Scientific Committee suggests the likelihood of another local extinction is greater than 50% in the next three generations due to habitat loss in one particular area.

Threats to Grevillea caleyi include habitat loss and fragmentation through development, inappropriate fire regimes, invasion from weeds and pathogens, disturbance through recreation activities and smothering from illegal rubbish dumping.^{[4][9][10][1]}