The 2017–18 season is Football Club Barcelona's 118th in existence and the club's 87th consecutive season in the top flight of Spanish football.

On 29 May, the club announced Ernesto Valverde would be the new Barcelona coach following the departure of Luis Enrique at the end of the previous season.

On 29 May, Barcelona and goalkeeper Marc-André ter Stegen negotiated a five-year contract extension lasting until 30 June 2022.

On 14 June, Fluminense centre-back Marlon Santos signed a three-year contract.

On 30 June, goalkeeper Jordi Masip's contract expired; he was not resigned and was therefore released.

On 30 June, the club activated a buyback clause for Everton's Gerard Deulofeu.

On 30 June, the club announced they have reached an agreement with Real Betis for the transfer of Cristian Tello for €4 million.

On 5 July, Barcelona and Lionel Messi negotiated a contract renewal that will keep Messi at the club until 30 June 2021. As of 30 August, the contract is reportedly still not signed by Messi.

On 7 July, Barcelona and Jérémy Mathieu agreed to mutually terminate the defender's contract. Mathieu subsequently joined Portuguese club Sporting CP on a free transfer.

On 13 July, Barcelona and Benfica reached an agreement for the transfer of right-back Nélson Semedo for €30 million.

On 21 July, Barcelona defeated Juventus 2–1 in a pre-season friendly. Neymar notched two impeccable first-half goals as the Catalans rolled past the Italian champions before 82,104 fans at a sold-out MetLife Stadium in the 2017 International Champions Cup. Giorgio Chiellini pulled one back for Juventus in the 63rd minute, not enough to keep the Ernesto Valverde era from beginning with a convincing win.

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