On a balmy night in 2013 at Wembley in north-west London, Heynckes led his Bayern Munich side past Bundesliga rivals Borussia Dortmund to the trophy.
The victory adorned the Bundesliga title his players had wrapped up with record six games to spare. A week after the triumph in London, Bayern beat Stuttgart to win the German Cup. It was an unprecedented treble for the Bavarians.
Heynckes, who had been in charge at the Allianz Arena since 2011, called it a day as a coach.
But four years on Heynckes, 72, is out of retirement and again leading Bayern. He took over from Carlo Ancelotti on 6 October and his first two games have produced eight goals.
On 14 October, Bayern thrashed Freiburg 5-0 to rise to second in the Bundesliga. On Wednesday night in the Champions League in front of their raucous faithful at the Allianz Arena, they swept past Celtic 3-0 to stay second in Group B three points behind pacesetters Paris Saint-Germain who boast nine points.
Bayern skipper Thomas Mueller put the hosts ahead after 17 minutes before goals by Joshua Kimmich and Mats Hummels sealed the victory.
Heynckes cracks the whip
Since his return, Heynckes has laid down the law with a list of rules restricting the use of mobile phones around the training grounds and insisting on punctuality. He has also told his well-paid stars to be courteous to Bayern employees and keep the changing rooms tidy. Players have also been ordered to dine together after training sessions.
Heynckes has also restored Mueller to a more advanced attacking midfield role, allowing him to roam just behind striker Robert Lewandowski.
"Thomas put in a good performance," said Heynckes after the victory. "He ran a lot, was very present and we saw the old Thomas Mueller."
He added: "Thomas is an established player, the captain and it's good to see him playing well again."
The Germany international struggled for form under Ancelotti and was often played out of position.
"The attitude was better," said the 28-year-old. "We were motivated after the win over Freiburg and wanted to use the momentum.
"We created a lot of chances in the second half against Celtic which we should have used."
Brendan Rodgers, the Celtic coach, said he had seen enough positives to give him hope for the return meeting at Parkhead in a fortnight.
"There were lots of elements, in particular the second half, where we played well and looked a real threat," he said.
"There was no denying we played against a top-class side and we didn't defend our box well enough when the crosses came in.
"I'd rather lose a game playing how we want to play, rather than defend for 90 minutes and still lose."