Supporters had high expectations they would witness a classic at the Levi’s Stadium.
But the first half was woeful and produced nothing of note whatsoever until Martial sprinkled some stardust on proceedings.
On the stroke of half time he took the ball and weaved through a combination of Daniel Carvajal and Luka Modric near the byline.
The French international could have gone for glory himself, but picked out the unmarked Jesse Lingard at the back post.
The finish into an open goal was straightforward and Lingard duly delivered, but all the went to Martial for creating the opening with his individual brilliance.
Martial has endured a difficult time at United since Mourinho took charge and was in and out of the team last season.
But this was a timely reminder of the remarkable skill he can produce and even Mourinho will have found it difficult not have been impressed.
But a reckless challenge from Victor Lindelof allowed Casemiro to equalise from the spot with 20 minutes remaining and take the game to a penalty shoot out, which United won after Real could only convert one of their five attempts and Daley Blind and Henrikh Mkhitaryan managed to hit the back of the net.
Hollywood legend Julia Roberts has developed a freakish obsession with United that has seen her visit training and the games so far.
The Oscar winner was here again and posted a message on social media before kick-off outlining how excited she was.
But even Roberts would have struggled to find the first half entertaining – because it wasn’t.
Lingard saw a long-range shot well saved by Keylor Navas while Real had just one shot at goal and even that was off target.
Both managers made a host of changes at half time and United continued to be the better team.
Romelu Lukaku just failed to connect with Daley Blind’s impressive cross from the left while Marouane Fellaini headed over from a corner.
At the opposite end, Real target David De Gea was in danger of getting sun stroke because he had so little to do in the United goal.
That was until Lindelof’s late and brainless challenge on Theo Hernandez offered Zinedine Zidane’s men a lifeline, which Casemiro took with some aplomb to convert from the spot.
United blew a golden chance to win the game in normal time with eight minutes remaining when Fellaini miscued from just six yards out.
The outcome will count for little in the long run, but it means United remain unbeaten in four games on this trip.
The one negative for United was when Ander Herrera limped off six minutes into the second half with what appeared to be a muscle problem down his left side.
