Rhytidiadelphus triquetrus can usually be found in well-drained sites of coniferous forests, on cliff shelves, boulders, and logs, occasionally epiphytic on tree trunks, or sandy-gravelly soils in beaches and streamsides of forests. It grows terrestrially on humus-rich substrates and is less common in lowland rainforests. It can sometimes be intermixed with H. splendens, R. loreus, and Kindbergia.
The stem is red, while the the leaves are yellow-green in color.
The lamina cells are elongate and the leaf margins are toothed. The marginal cells are not otherwise differentiated from the rest of the laminal cells.
The seta is sometimes bent near the apex at maturity, resulting in a nodding sporangium.