The Sulu hawk-owl is an earless species. The males and females look much alike. The Sulu hawk-owl is one of the biggest in the Philippine hawk-owl complex.
The Sulu hawk-owl can be found in forest areas up to 1800 metres, although they mostly reside in areas below 1000 metres above sea level. Its natural habitats are subtropical or tropical moist lowland forests and subtropical or tropical moist montane forests. This species mates around February. The nests can be found in hollow trees.
- BirdLife International (2017). "Ninox reyi". The IUCN Red List of Threatened Species. IUCN. 2017: e.T22725499A110051404. doi:10.2305/IUCN.UK.2017-1.RLTS.T22725499A110051404.en. Retrieved 15 January 2018.
- Kennedy, R.S., Gonzales P.C., Dickinson E.C., Miranda, Jr, H.C., Fisher T.H. (2000) A Guide to the Birds of the Philippines, Oxford University Press, Oxford.