All completed Celtic transfers so far in 2025-26 - listed

The first addition of the January window was Julian Araujo, who joined on loan from Premier League side Bournemouth. The Mexico international, who was once on the books at Barcelona, previously played for MLS team LA Galaxy.

Interim manager Martin O'Neill - the Irishman in the temporary role for the second time following the abrupt tenure of Wilfried Nancy - jokingly said that Celtic need "about 56 players".

"We need the players in and as quickly as possible," O'Neill told reporters when asked about the window. "I would be hoping for it [to be busy] - but if the board were to listen to me then we would have about 56 players. It's a difficult window in terms of buying players."

Hayato Inamura left the club to join FC Tokyo on loan, while Daizen Maeda has been linked with a permanent move away, with a host of Bundesliga clubs among his suitors.

Celtic’s summer 2025 transfer window saw a steady flow of both arrivals and departures. Among the key signings was the return of Kieran Tierney, who rejoined the club on a free transfer from Arsenal, adding proven quality and a deep connection to the club at left-back.

Swedish forward Benjamin Nygren arrived from Nordsjælland in a deal worth around £2 million, bringing versatility and attacking depth. Goalkeeper Ross Doohan signed on a free from Aberdeen, while young talents like Callum Osmand from Fulham and Isaac English from Greenock Morton were added with an eye on future development.

Celtic signed defender Hayato Inamura from Japanese J1 League side Albirex Niigata. Shin Yamada has also arrived at the club from Japan. Man City sent Jahmai Simpson-Pusey to Celtic on a season-long loan. On deadline day, they added Sebastian Tounekti in a £5.2m deal, while experienced Nigeria international Kelechi Iheanacho joined from Sevilla on a free transfer.

On the departures front, Scott Bain joined Falkirk on a free transfer, while Greg Taylor completed a move to Greek side PAOK.

Promising youth player Daniel Cummings signed for West Ham, and others such as Joey Dawson and Matthew Anderson also left the club.

Maik Nawrocki is reportedly heading to Hannover on loan, and Nicolas Kühn left for Serie A club Como in a deal that could fetch around £17 million. Ireland international striker Adam Idah departed for Championship outfit Swansea City, while Stephen Welsh joined Motherwell on loan.

Gustaf Lagerbielke has confirmed his departure from Celtic to sign for Braga on a £2m deal. 

Luis Palma and Kwon also left the club this summer.