Cristiano Ronaldo had been booked earlier in the game, before receiving a straight red card
Ronaldo, 39, was shown a straight red card on 86 minutes after appearing to swing his elbow twice into the chest of Ali Al Bulayhi, who fell to the floor.
The Portugal international then appeared to raise his first towards the referee before leaving the field.
It is Ronaldo's first red card since his move to Al-Nassr in December 2022.
Al-Nassr were trailing 2-0 at that stage after goals from Salem Al-Dawsari and Malcom, with former Liverpool forward Sadio Mane pulling one back in stoppage time.
Three-time winners Al-Hilal will play Al-Ittihad in the final on Thursday.
Al-Ittihad beat Al-Wehda 2-1 in their semi-final earlier on Monday thanks to goals from former Real Madrid captain Karim Benzema and Morocco forward Abderrazak Hamdallah.
-- Courtesy of BBC Sport