Lee Jung-jae
as Seong Gi-hun / 'No. 456'
Park Hae-soo
as Cho Sang-woo / 'No. 218'
Jung Ho-yeon
as Kang Sae-byeok / 'No. 067'
Wi Ha-jun
as Hwang Jun-ho
Oh Young-soo
as Oh Il-nam / 'No. 001'
Heo Sung-tae
as Jang Deok-su / 'No. 101'
Kim Joo-ryoung
as Han Mi-nyeo / 'No. 212'
Anupam Tripathi
as Ali Abdul / 'No. 199'
Lee You-mi
as Ji-young / 'No. 240'
Kwak Ja-hyung
as 'No. 278'
Kim Seo-hyeon
as 'No. 244'
Kim Young-ok
as Gi-hoon's mother
Yoo Sung-joo
as 'No. 111'
Yun Seung-hun
as 'No. 369'
Kim Yun-tae
as 'No. 069'
Kim Dong-hyun
as 'No. 196'
Moon Byung-joo
as 'No. 021'
Im Gi-hong
as 'No. 322'
Lee Doo-seok
as 'No. 062'
Gong Yoo
as Man at the station
Lee Byung-hun
as Hwang In-ho
Kang Mal-geum
as Gi-hoon's ex-wife
Cho Ah-in
as Seong Ga-yeong
Woo Young-taek
as 'No. 194'
Lee Ji-ha
as 'No. 070'
Lee Sang-hee
as 'No. 017'
Yang Mal-bok
as 'No. 453'
Geoffrey Giuliano
as VIP 4
Daniel C Kennedy
as VIP 2
John D. Michaels
as VIP 1
Park Si-wan
as Sae-byeok's brother
Yoon Don-sun
as 'No. 119'
Min Tae-yul
as 'No. 271'
Kim Pub-lae
as Loan shark
Kim Gyeong-min
as Racetrack man
Kim Gye-sun
as Dorm owner
Kim Min-sik
as Police 2
Lee Dong-yong
as Police 1
Anwesha Purkayastha
as Ali's wife
Lee Seo-hwan
as Gi-hoon's friend
Hong Woo-jin
as 'No. 118'
Heo Dong-won
as ○ Mask
Yoon Ju-man
as △ Mask / Surgery Room Guard 2
Hwang Yeon-hui
as 'No. 308'
Jeong Woo-hyuk
as 'No. 096'
Son Young-soon
as Flower seller
Lee Jeong-heon
as Banker
Park Ji-hoon
as 'No. 250'
Park Sun-a
as 'No. 107'
Lee Jung-jun
as □ Mask
Yun Yeong-keol
as Surgery Room Guard
Lee Han-sol
as No. 324