The comfortable 4-1 win over Al Ain means Real have won the prestigious trophy for three years in a row and a record four times in total.
Sergio Ramos almost always pops up with a goal in big finals, and this one was no different as he headed in Luka Modric's 78th-minute corner to make it 3-0.
The centre-back has now won an impressive 20 trophies at Madrid, but fans inside the stadium could be heard loudly booing him whenever he touched the ball against Al Ain.
It lasted throughout the entire final, Ramos himself reacted in his goal celebrations, and now Spanish media have explained the specific reason why he got booed.
Ramos key at both ends in Club WC final
Prior to his goal which pretty much sealed Real's triumph, Ramos prevented his team from conceding what looked like a certain goal with a super goal-line clearance.
During his goal celebration, the Madrid captain put his hands to his ears and made a "shushing" gesture to the crowd - two actions that only enraged supporters even further.
Why Ramos got booed by fans at Club WC final
The match took place at the Zayed Sports City Stadium in Abu Dhabi, United Arab Emirates, a little over an hour away from Al Ain's home ground - but that's not why fans booed.
We all remember that the 32-year-old was involved in the incident which saw Salah dislocate his shoulder and leave the 2018 Champions League final in tears.
Football fans in the UAE clearly haven't forgiven Ramos yet for his part in Salah's injury, which put his participation in Egypt's first-ever World Cup campaign at risk.
Marca claimed that the "idol status of Salah" in the Arabic community meant that fans were eager to let Ramos know where their allegiances lie and what they think of the Spaniard.
Ramos gets last laugh with another trophy
Whether you love Ramos, hate Ramos or are somewhere in between, no one can deny that the man who's played a whopping 590 times for Los Blancos is a serial winner.
Salah will be hoping to follow Ramos' habit of winning trophies himself this season by scoring the goals to fire Jurgen Klopp's Liverpool to their first league title in over 28 years.
What do YOU make of Abu Dhabi fans continuing the feud between Ramos and Salah during the Club World Cup final? Be sure to leave YOUR thoughts in the comments box below!