The right-back landed at Manises airport just after 1am and will undergo a medical later today before reporting to new head coach Carlos Corberán.
The plan is to have him registered in time for Saturday's game against Celta Vigo, giving Maffeo a chance to feature in Valencia's league opener — a timely arrival for a squad that currently has no other recognised right-back available.
Maffeo joins on a season-long loan from Olympiacos, with a purchase option set at just over €3m, a figure notably close to what the Greek club paid Mallorca for him only two months ago. His contract in Piraeus runs until June 2029, meaning this is very much a stopgap arrangement rather than the start of a longer-term commitment from either side.
Speaking to reporters moments after landing, Maffeo described the move as the culmination of a long-held ambition.
"It's a dream, it's something I've wanted," he said. "It's been in the works for a long time. From the very first day I knew this option existed, I wanted to come.
"Even before signing for Olympiacos I knew it could happen, and in the end it has. It's an option that came up that suited me completely. Nothing strange happened in Greece."
The defender also made clear he was ready to feature immediately if called upon this weekend.
"I'm available for the manager, for the team," he said. "Everyone knows how I am — I'm going to give everything, and I'm really happy to be here. I've come here to compete at the highest level, to try to stay here, which is what I want — to stay here for the future, and that's it. I'll compete the same way against Madrid as against everyone else. What motivates me is playing for Valencia CF."
The move resolves an urgent problem for Corberán, whose squad had been left without a fit senior option at right-back following an injury to Dimitri Foulquier and the summer departure of Thierry Rendall.
Maffeo already knows LaLiga well from his time at Mallorca, where he made 160 appearances, scoring five goals and providing 15 assists, and Valencia's coaching staff are said to view him as a ready-made solution rather than a player who will need time to adapt.
The Catalan-born defender came through Espanyol's academy before a path that took him through Manchester City, Girona, Stuttgart, Huesca and Mallorca, and family ties to Valencia are understood to have made the move easier to agree on personal terms.