Commons, who grabbed a last-gasp equaliser at Ross County in the SPL on Saturday, volleyed the visitors into the lead with less than two minutes on the clock following a cross from Samaras.
Hoops goalkeeper Fraser Forster made a series of saves as the Swedish champions fought back but in the 75th minute Samaras put Celtic in the driving seat for next week’s second leg in Glasgow when he headed in a Commons corner.
Neil Lennon’s side might have rode their luck at times but they could have won by more in the end and now face the tantalising prospect of mixing with the elite clubs in Europe for the first time since the 2008/09 season.
There were significant changes to both line-ups as skipper Scott Brown and striker Gary Hooper shrugged off their respective hip and hamstring injuries to start for Celtic, while defender Thomas Rogne replaced Kelvin Wilson.
Serbian striker Nikola Djurdic, who signed for Helsingborg on loan from Norwegian side Haugesund yesterday, made his debut for the hosts while former Rangers midfielder Alejandro Bedoya started in midfield.
However, all of Age Hareide’s pre-match plans went up in the air when Celtic stormed into an early lead.
Samaras picked up a pass from Joe Ledley on the left and, when his cross came into the middle, the unmarked Commons slammed it past the helpless Par Hansson from 12 yards.
The strike changed the whole complexion of the tie, although the Parkhead side were fortunate to have their lead intact by the time the interval whistle sounded.
It was the 12th minute before Helsingborg really threatened Forster, although the Hoops keeper dealt with Djurdic’s angled shot from 14 yards with ease down at his left post.
Four minutes later the Geordie made a more impressive save with his feet from Bedoya’s low drive after the United States international had been put through by Thomas Sorum.
It was another warning for the Celtic defence and in the 21st minute Forster had to come to the rescue again when Sorum was played in by Christoffer Andersson, the keeper this time blocking the striker’s all-too-casual chip.
There was more concern for Lennon three minutes later, following a Celtic corner which had been cleared, when hesitant Hoops defender Adam Matthews was robbed by May Mahlangu on the halfway line, leaving the Helsingborg midfielder to go clean through on goal.
However, Mahlangu slowed down as he entered the box, allowing the Wales international to atone for his mistake with a great saving tackle.
As the noisy home support kept up their encouragement, Bedoya headed an Andersson cross wide of the target before Djurdic fired over from 16 yards after Celtic midfielder Beram Kayal was careless with an attempted clearance.
Forster was then booked by Portuguese referee Olegario Benquerenca for time-wasting at a goal-kick, joining defender Charlie Mulgrew who had been cautioned for a foul on Djurdic.
Winger James Forrest replaced Kayal for the start of the second half, with Commons moving into the middle to support Hooper. However, the pattern of the first half continued and in the 50th minute Forster had to deal with Mahlangu’s 25-yard drive before Andersson fired just wide with a shot from a similar distance.
The hosts still looked vulnerable in defence, though, and when Forrest picked out Ledley with a cross the Welsh midfielder skimmed the crossbar with a header from six yards.
Just after the hour Rogne was booked for handling the ball when Sorum tried to flick it over his head 25 yards out, but Jere Uronen’s free-kick was comfortably saved by Forster.
After Ledley picked up an injury and was replaced by Wilson, Helsingborg substitute David Accam ballooned the ball over the bar from 14 yards.
In the 73rd minute Forster made yet another save from Bedoya, this time from a header from Uronen’s cross.
Celtic’s sucker punch came when Commons’ corner from the right was met by Samaras at the back post and he headed past Hansson from a couple of yards to double the visitors’ lead.
The goal knocked the stuffing out of Helsingborg, who should have been dead and buried three minutes later when Samaras ran through on goal but the Greece striker curled his right-footed shot wide of the far post.
In the 86th minute Commons released Forrest and he slammed his angled shot straight at Hansson, before the Scotland winger set up Mulgrew who curled a right-footed effort off the top of the bar.