The Bavarian giants had few problems against Moroccan champions Raja as Bayern grabbed both goals inside the opening 22 minutes from Brazil centre-back Dante, then midfielder Thiago.
Having become the first German team to win the treble of Champions League, Bundesliga and German Cup titles last season, Bayern now add the Club World Cup to the UEFA Super Cup title they won in August.
This was the third time Bayern coach Pep Guardiola has won the Club World Cup after lifting the trophy with Barcelona in 2009 and 2011.
"2013 is now finished and it's behind us," said Guardiola.
"Five titles is really a great achievement. I am proud of this club and for all the people involved."
He added: "Since my arrival I have tried to care for the heritage of the club.
"Now I will try and add other things that I hope will be positive for the club. We have to turn to the future."
Raja coach Faouzi Benzarti said he was proud of his team's efforts.
"I think my players were a little nervous in the first half, with the crowd and with the king being present," he said.
"But to lose to Bayern by only 2-0 is very honourable."
Bayern winger Franck Ribery was voted player of the tournament. The France winger must wait until January 13 to find out if he has beaten Lionel Messi and Cristiano Ronaldo to the Ballon d'Or.
Even without injured Germany star Bastian Schweinsteiger and Netherlands winger Arjen Robben, Guardiola's Bayern had too much firepower for Raja at the 45,000 sell-out Marrakech Stadium.
Just as they had done in Wednesday's 3-0 semi-final win over Asian champions Guangzhou Evergrande, the Germans dominated throughout.
Bayern took the lead after only seven minutes when Germany star Jerome Boateng found his centre-back partner Dante onside with the goal at his mercy.
The Raja offside trap had failed and with his second touch, Dante hit the back of the net.
Munich doubled their lead on 22 minutes when left-back David Alaba won the ball, then laid it back for Thiago, who blasted his shot into the top right-hand corner from the edge of the area.
Bayern gifted Casablanca a strong first-half chance when goalkeeper Manuel Neuer's lazy clearance was snapped up by Chemseddine Chtibi who fired wide from 26 metres out with 38 minutes gone.
The Moroccans have earned admirers for a tremendous run which saw them beat Auckland City, Monterrey and Atletico Mineiro en route to the final where they had plenty of home support.
With time running out, they so nearly grabbed a consolation goal.
After substitute Vianney Mabide's shot was parried by Neuer, Raja's captain Mouhcine Moutouali fired the rebound over the bar six minutes from time.
Bayern are on course to defend all their titles in 2014 having reached the Champions League knock-out phase as group winners.
They are also seven points clear in the Bundesliga with a game in hand having broken or equalled 25 German league records last season.
In the third-place play-off earlier Saturday, Atletico Mineiro defeated Guangzhou 3-2 thanks to a last-minute strike from substitute Luan.
The Brazilians played the closing minutes of the match with 10 men after veteran star Ronaldinho, who had scored his team's second goal, was red-carded.