Foakes arrived at the crease with his side wobbling at 62 for four but turned in a nerveless performance to reel in the winning target of 199 in Malahide.
He finished with 61 not out in 76 balls, a priceless knock that spared England the existential angst of kicking off World Cup year with defeat to a side who have not even qualified for the tournament.
All things being equal, it was an innings that should act as the Surrey man's calling card but, rather than making a late bid to gatecrash the squad, he was merely thankful to earn his cap.
With the rested duo of Jos Buttler and Jonny Bairstow untouchable in the side, Foakes was still on the outside until Sam Billings' shoulder injury saw him earn a late call.
Asked if he could force his way into England's 50-over plans, the 26-year-old offered a surprising conclusion.
"Probably not, no," he said.
"Jos is probably the best keeper batsman in the world, Jonny is probably second, if not first. It's ridiculous. This is great but something I didn't expect.
"It's really exciting to make your debut, especially in ODI cricket because I didn't really think I'd make my debut. Just to get the game has been great."
Foakes knows exactly how it feels to be dropped, having lost his Test place in the West Indies just three games after a century in his maiden international innings.
His fighting qualities and cool head mark him out as a special character, though, and one whose contribution alongside Tom Curran (47 not out) proved priceless.
"It was probably not the position you think you're going to come into with this one-day team, it was one of those rebuilding jobs and I guess that suited my game a little bit," he said.
"I just had to get my head down and fight it out, it was a bit of a grind. When it's that sort of situation you know what the job is and you don't go too far out of your comfort zone. It's just about batting and soaking up the pressure
Foakes had already left his mark on the game before taking to the crease, taking an unusual stumping to dismiss Andrew Balbirnie. He waited a couple of beats after taking the ball down leg side and whipped the bails off as Balbirnie's trailing leg lifted.
Ireland skipper William Porterfield did not appear entirely happy with the opportunistic nature of the dismissal.
"How long do you wait? We'll be playing 15 hour games if you wait that long," he said.
"You can say it was great wicketkeeping or you can say it's a bit of a grey area. The ball is pretty much dead, he wasn't going anywhere or over balanced. If we do that all day it's gonna be a pretty long game."
Foakes had a more prosaic explanation, adding: "I was happy with it. It was quite wide down leg, but I got it back to the stumps.
"When it's a sweep you think they might fall over and I just saw he lifted his foot and nicked them off."
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