Murray was at the side of the court cheering on his team-mate after getting Great Britain off to a flying start against the United States with a resounding win over Donald Young.
The visitors looked like drawing level after Isner took the first two sets 7-6 7-5 but Ward then launched an extraordinary comeback to win the next two and set up a marathon decider.
And Murray was as vocal as anyone in the raucous 7,500 crowd at the Emirates Arena in Glasgow when Ward triumphed on his sixth match point to edge the final set 15-13.
Murray later wrote on Twitter: “Time to remove every item of clothing and run through the streets of Glasgow.. Absolute farce from @JamesWardtennis” and his friend and team-mate was delighted with the Scot’s backing.
“To have Andy there living every point with you is something I haven’t really experienced before and that’s why it was a special moment,” Ward said.
“He is probably my best friend in tennis and we did a lot of training in Miami. He knows how hard I have worked and I know how hard he works. So it was good to share the moment together.”
Ward admitted that training in Miami had paid off against the man who won the longest tennis match in history.
The big-serving American prevailed in an 11-hour, five-minute Wimbledon contest with Nicolas Mahut in 2010 but Ward showed no sign of wilting in their near-five-hour encounter in Scotland.
The 28-year-old said: “Look, five hours with John isn’t easy and it’s more mentally tiring.
“It wasn’t like each rally was long because he was serving a lot of aces and a lot of unreturnables. But you need to be there each point because you never know when your chance is going to come.
“He can serve four aces and then the next game you could have a break point and you have to be there all the time. All the hard work pays off.”