Gareth Bale came off the bench to score Real Madrid’s winning goal with his first touch in their Fifa Club World Cup semi-final against Al Jazira.
Bale, 28, scored moments after coming on for only his second appearance since suffering a calf injury in September.
Al Jazira had taken a first-half lead through Brazilian forward Romarinho.
Mbark Boussoufa then had a strike ruled out for offside by the virtual assistant referee before Cristiano Ronaldo equalised for Madrid.
The Portuguese is now the all-time top scorer in Fifa Club World Cups with six – taking him past Lionel Messi, Luis Suarez and Cesar Delgado’s five.
The Club World Cup features Fifa’s six reigning confederation champions plus the league winners, Al Jazira, of the host country, United Arab Emirates.
Zinedine Zidane’s side will now play Brazilian side Gremio in Saturday’s final.
Bale said: “It is great to get a goal. When you come on you like to make an impact like that. The most important thing is to get the win and get into the final.
“I have still got some way to go get back to full fitness. It takes time but I have to be patient and listen to my body.
“Video technology? I don’t like it. Football is better without. I am sure people above will make the decision, not me.”
Before falling behind Madrid had two first-half goals ruled out for infringements.
Karim Benzema’s header was disallowed for a foul by Ronaldo in the build-up and Casemiro was denied after the video assistant referee gave offside against Benzema.
In between Ronaldo’s equaliser and Bale’s winning goal, Benzema hit the post twice.
Real Madrid won the competition in 2014 and 2016 and a third success on Saturday would take them equal with Barcelona for the record amount of tournament wins.