The 23-year-old Greek international is already in Germany after boarding a flight to Dortmund on Sunday morning.
The move comes just days after Dortmund abandoned their prolonged pursuit of Cologne winger Said El Mala, having reportedly raised their offer beyond €55m without resolving a dispute over the guaranteed portion of the fee. According to Greek outlet Gazzetta, Dortmund and PAOK have moved close to a final agreement worth up to €30m including bonuses for Konstantelias, who would sign a four-year contract worth around €3.2m per season.
The Ruhr Nachrichten reported by midday that the winger had landed in Dortmund, though the same outlet cautioned that negotiations between the clubs were not yet fully concluded.
Konstantelias, who came through PAOK's youth system before a brief loan at Belgian second-tier side Eupen, has been a key figure in Thessaloniki since establishing himself as a regular in 2022, contributing 70 goal involvements in 190 competitive appearances and helping the club win its first Greek title in five years in 2024.
His departure has not gone down well with PAOK's supporters, with the influential "Gate 4" ultras group publicly demanding the club keep hold of him, a group that previously helped scupper a move to VfB Stuttgart a year ago.
At Dortmund, Konstantelias would link up with fellow Greece international Konstantinos Karetsas, who joined the club this summer for a fixed fee of €30m from Belgium and is said to have spoken positively about life at the club to his international team-mate.
Dortmund's sporting director duo of Lars Ricken and Nils-Ole Book have been searching for offensive reinforcements following Karim Adeyemi's move to Barcelona, with Konstantelias's pace and ability to beat opponents one-on-one seen as fitting the profile they have been targeting throughout the summer.