[1][2] It is dark brown, occasionally with some reddish, but lacking the light-coloured sections usually seen in its close relative, the northern Luzon giant cloud rat (P. pallidus).

The southern giant slender-tailed cloud rat is a large rodent that has a total length of about 67–75 cm (26–30 in) and weighs 1.45–2.1 kg (3.2–4.6 lb).

[2] Equally at home high amongst the branches of a tree as on the forest floor, the southern giant slender-tailed cloud rat is a slow-moving animal only active at night, spending the day in hollow trees or logs.

Their diet consists primarily of tender, young leaves, but fruit is also reportedly eaten.

The young are born in the hollow of a standing or fallen tree, or in a hole in the ground.