Otus longicornis has probably become rare as a result of habitat loss.
Otus longicornis is restricted to forest above 350 m on Luzon in the Philippines, where it was recently found in Quezon National Park , and on Mounts Cetaceo and Dipalayag (Sierra Madre) in lower montane forest, 700--1,500 m.
Otus longicornis is listed as "Vulnerable" by the IUCN Red List.