Real Madrid, the Spanish League champion, dominated.
The first goal came in the 22nd minute, when Gonzalo Higuain split two Celtic defenders and fed Jose Callejon, who scored into an open net.
Karim Benzema added an insurance goal in the 67th minute with a nice move past Adam Matthews then a shot to the far left corner of the net that beat goalkeeper Lukasz Zaluska.
In the 31st minute, Real Madrid had a chance to extend its lead, but Cristiano Ronaldo was denied by Zaluska.
Ronaldo substituted out in the 58th minute along with several other Real Madrid players.
Celtic's best chance was in the 45th minute when Joe Ledley slipped past a defender and fired a 20-yard shot about a foot over the crossbar.
Celtic lost more than the game. Dylan McGeough was removed from the field on a stretcher after a collision with Real Madrid's Nuri Sahin when both went up for the ball and Sahin caught McGeough on the chin with his left shoulder.
McGeough moved his arms across his chest before he was taken to a hospital to show he was conscious.
"They think (McGeough suffered) a fractured jaw," Celtic coach Neil Lennon said. "He's in a distressing state when I left him.
Saturday was the last in a nine-game North American series, organized by Major League Soccer. It also concluded a grueling four-game stretch in nine days for Real Madrid, which went 4-0 and outscored its those opponents by a combined 14-3.
Celtic, the reigning Scottish Premier League champions, began its league season last weekend and is scheduled to play in Finland on Wednesday. Regular goalkeeper Fraser Forster did not play against Real Madrid and star forward Georgios Samaras did not make the trip.