The forest batis was described by the English ornithologist George Ernest Shelley in 1889 and given the binomial name Pachypora mixta.

[5] The forest batis is a small species measuring 9.5–10 cm (3.7–3.9 in) in length and weighing 10.5–14.2 g (0.37–0.50 oz).

[6] The adult male has bluish grey upperparts with a black mask across the face, a white spot on the lores and white spots on the rump which are revealed when the long feathers are fluffed out.

[7] The habits of the forest batis are little known, there have been indications of breeding behaviour in May and June in Kenya, September and October in Tanzania and a single nest with a clutch of 2 eggs has been recorded.

Calling males make a repetitive, slow series of hu-hu-hu-hu whistles and they puff their white throat feathers out while performing this song.