The two teams finished side by side in the league phase, with Celta finishing one place higher in 16th having also beaten PAOK 3-1 in October.
The Spanish side fashioned the first two big chances of this game when visiting captain Iago Aspas played a lovely through-ball to Williot Swedberg, who was subsequently twice denied by Antonis Tsiftsis from close range.
Oscar Mingueza was the next Celta player to be left frustrated as his strike from an angle flew well over the bar, but the visitors eventually made the most of their pressure shortly after the half-hour mark.
PAOK defender Dejan Lovren’s clearance was redirected by Celta right-back Javi Rodriguez to Miguel Roman, whose wonderful improvised flick over Magomed Ozdoyev’s head allowed Aspas to finish coolly.
Celta doubled their lead nine minutes later, too, with Roman heavily involved once more. He clipped a wonderful pass to Swedberg, and after laying the ball off to Aspas, the 22-year-old dashed into the box to dispatch the resulting cross.
An offside flag deprived Sergio Carreira of the chance to make it 3-0 on the stroke of half-time, but Celta will have been extremely happy with their display in the opening 45 minutes regardless.
Without main goalscorer Giorgos Giakoumakis through suspension, PAOK were still looking for their first shot on target when the teams re-emerged, but they continued to struggle in the final third against a side intent on keeping a clean sheet.
With around an hour on the clock, PAOK did finally force Celta goalkeeper Ionut Radu into action through Alexander Jeremejeff, but the Romanian was equal to the attempt.
Celta substitute Ferran Jutgla then thought that he had got on the scoresheet, but like Carreira, he was thwarted by the linesman’s flag.
Not long after that, the hardworking Jeremejeff halved the deficit with a lovely volley on the stretch to set up a grandstand finish at Toumba Stadium, this time surviving an offside call.
Despite some nervy late moments, Celta held on to end a five-game winless run in all competitions (D3, L2) and will now have a spring in their step ahead of the second leg in Galicia.
PAOK, meanwhile, have won only one of their past four, failing to score in two, and will therefore need to improve significantly if they are to turn this tie around next week.
Flashscore Man of the Match: Carl Starfelt (Celta Vigo)
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