The plant was first described as Epacris sinclairii in 1864 by Joseph Dalton Hooker, based on specimens collected by Andrew Sinclair.

[3] In the 1906 Manual of the New Zealand flora, Thomas Cheeseman described Sinclair's tamingi as Epacris pauciflora var.

[3][4][5][7] E. sinclairii can grow as a shrub or as a small tree, reaching a maximum height of 9 m (30 ft) (but typically much smaller).

[3] The species is endemic to New Zealand, known from two locations: the Mount Hobson massif of central Great Barrier Island, and the Upper Kauaeranga Valley of the Coromandel Peninsula.

E. sinclairii grows exclusively in rhyolitic soil, typically found in high elevation humid forest and surrounding areas, and can occasionally be an epiphyte.