According to reports, the Parkhead side had a bid of around £3.5m accepted on Friday with the 23-year-old attacker set to travel to Glasgow over the weekend to put the finishing touches on a four-year contract.
Palma, who was previously linked with Rangers, also had offers from clubs in Saudi Arabia and the US but expressed a preference to remain in Europe and will sign for last season's Scottish champions.
He has started the Greek season in red-hot form with two goals and three assists in five appearances continuing his impressive numbers from last season which saw him involved in 21 goal contributions across 36 matches.
Palma will become Celtic’s seventh summer signing but is unlikely to be the last new arrival at Parkhead before the transfer window closes on Friday with manager Brendan Rodgers looking to recruit another centre-half after a spate of injuries to Cameron Carter-Vickers, Maik Nawrocki and Stephen Welsh left him with a depleted backline.
One player who will not be joining Celtic, however, is Arsenal defender Kieran Tierney who is closing in on a move to Real Sociedad. The 26-year-old Scotland left-back has reportedly agreed a season-long loan switch to the La Liga outfit after being exiled from Arsenal's matchday squad for the opening two fixtures of the Premier League campaign.
He had been linked with Newcastle United earlier in the window and there was also talk of a potential return to Celtic under his previous manager Rodgers but reports on Friday claimed that a deal with Sociedad – who have qualified for the Champions League group stages – is all but done with Tierney set to undergo a medical this weekend.
Socieded will pay a loan fee and cover his full salary, but there is reportedly no option to buy for the Spanish side included in the deal, meaning that Tierney will likely return to Arsenal next summer, where his contract runs until 2026.
Should the move go through it will be welcome news for Scotland head coach Steve Clarke ahead of next month’s international matches against Cyprus and England with one of his most important players now likely to earn more regular game-time in one of Europe's top leagues.