The deal comes as Barcelona continue working to reduce their wage bill and generate income before the financial year closes on 30 June. The club are eager to return to La Liga's 1:1 spending rule, which would give them greater flexibility in the transfer market.
Pena's departure brings an end to a long association with Barcelona. The 27-year-old joined the club's famous academy in 2012 as a teenager and spent 14 years in the Catalan system.
The goalkeeper enjoyed a run in the first team during the 2024-25 campaign after Marc-Andre ter Stegen suffered a serious injury. However, once veteran goalkeeper Wojciech Szczesny established himself as the number one choice, Pena struggled to regain his place in the side.
Last season, Pena spent time on loan at Elche, making 16 appearances before returning to Barcelona. His return now appears to have been only temporary, with a permanent switch to Greece set to be completed.
Reports indicate that Barcelona and Panathinaikos have finalised an agreement, with the Spanish club expected to receive around 3 million euros for the transfer. Earlier suggestions claimed Barcelona might allow the goalkeeper to leave without a fee, but Panathinaikos have agreed to pay for the move.
Pena is expected to travel to Athens shortly to undergo a medical examination before signing his new contract.
