Medicosma forsteri is a tree that typically grows to a height of. The leaves are arranged in more or less oppositepairs and are narrow elliptical to narrow egg-shaped with the narrower end towards the base, long and wide on a petiole long. The flowers are arranged singly or in small groups up to long and are sessile or on a pedicel up to long. The sepals are long and densely covered on the outside with soft hairs flattened against the surface. The petals are cream-coloured, about long, densely covered with flattened hairs on the back and part of the front. The remnants of the petals remain on the fruit, increasing in size to about. Flowering has been observed in April and the fruit is a follicle about long.