IUCN said it has evidence that the number of mature tigers is "likely less than 250," declining by 25% in one generation (seven years).
It said the tigers were categorised in the "red list" as there were no pockets of forest in Malaysia with an estimated population of 50 or more mature tigers.
IUCN’s list is considered the world’s most comprehensive source of information on wild animals and plants and the level of threat they face.
“This acknowledgement of our research is sadly, a tacit recognition that our tigers face a bleak future,” Malaysian Conservation Alliance for Tigers (MYCAT) general manager Dr Kae Kawanishi said in a statement Tuesday.
Kawanishi said the two biggest causes for the decline in the tiger population were poaching and loss of habitat.
The tigers were hunted for their bones which are believed to have anti-inflammatory properties. Tiger teeth, claws, skin and meat also fetch high prices on the illegal market.
A study by Wildlife Trade Monitoring Network (Traffic) revealed that parts equivalent to at least 94 tigers were recovered from 33 seizures from 2000 to 2013 in Malaysia.
The Malayan Tiger was recognised as a new sub-species in 2004.
The Malayan Tiger now joins other critically-endangered animals such as the Namdapha flying squirrel and the Asiatic cheetah.
The remaining tiger population is estimated to be only 5,000-7,000 with three of the traditional eight subspecies - the Javan, Bali and Caspian tigers - becoming extinct in the mid to late 20th century.
Kawanishi called on Malaysians to voice their concerns and show their support for their wild tigers.
To make a report on wildlife crime, contact the Wildlife Crime Hotline at 019-356 4194.