Vissel Kobe are the defending champions, having won their second league title in a row on the last matchday of the 2024 season.
Júbilo Iwata, Hokkaido Consadole Sapporo, and Sagan Tosu, were relegated as they finished 18th, 19th, and 20th respectively in the previous season, ending their one, eight, and 13-year stays in the top flight respectively.
Three teams were promoted from the 2024 J2 League: Shimizu S-Pulse, who won the title and returned to J1 after a two-year absence, Yokohama FC, who finished second, returning to the J1 after just a season playing in the J2 League, and Fagiano Okayama, who finished fifth and won the play-offs; they will play in the top division for the first time in their history.
From the 2021 season, there are no limitations on signing foreign players, but clubs can only register up to five of them for a single matchday squad.
[20] Players from J.League partner nations (Thailand, Vietnam, Morocco, Malaysia, Cambodia, Singapore, Indonesia) were exempted from these restrictions.