Swietenia macrophylla is a very large tree, reaching a height of 30-40 m and a girth of 3-4 m; in favourable conditions it can reach 60 m high and 9 m girth. Trunk straight, cylindrical, with a buttressed base; bark rough, flaking off in small patches. Leaves paripinnate, up to 60 cm long; leaflets 6-16, ovate, lanceolate, acuminate, slightly oblique, light green or reddish when young, dark green and shining when mature, up to 20 cm long, with 8-12 pale, secondary nerves. Flowers 8 mm across, in narrow supra-axillary panicles about 8-13 cm long and fragrant; petals greenish-white, oblong, 4 mm long, rigidly pointed. Fruit a woody capsule resembling a large inverted club, about 12.5 x 7.5 cm, erect.
S. macrophylla is found in all forest types, from the edge of the pine savannah to the climax rainforest, but mostly in mixed hardwood forest belts, along riverbanks, on deep alluvial soils of considerable fertility. It occurs scattered or in small groups, but densities of more than 4-8 trees/ha are rarely encountered. In tropical America, it is among the pioneer species reoccupying degraded agricultural land. It has been shown that teak is outcompeted by S. macrophylla in a mixed stand. In the Philippines, S. macrophylla is reported to be very firm in wind, resistant to cyclones. The species has some weed potential and may invade native forest communities, especially following disturbance. It should not be planted in close proximity to areas of high nature conservation significance.