Leptospermum macrocarpum is a shrub that typically grows to a height of 2 m (6 ft 7 in) and has thin, rough, sometimes gnarled bark and young stems that are hairy at first.

The flowers are greenish white, pink or dark red, 15–30 mm (0.59–1.18 in) wide and arranged singly on short side shoots.

Flowering occurs from October to December and the fruit is a woody capsule 15–20 mm (0.59–0.79 in) wide that is not shed when mature.

macrocarpum and published the description in the Linnean Society of New South Wales from specimens collected by Jesse Gregson on Mt Tomah in 1897.

[9] Leptospermum macrocarpum grows in heath or forest on exposed sandstone in the Blue Mountains.