In August 2018, Wagué completed a transfer from Eupen to FC Barcelona, for a fee of €5 million. He initially joined the reserves ahead of the 2018–19 season.[7] On 13 January 2019, Wagué scored his first goal for Barcelona B in a 2–0 win at the Miniestadi against CD Alcoyano.[8]
Barcelona manager Ernesto Valverde named Wagué as one of the five promising young players to whom he hoped to give first team opportunities.[9] Wagué made his senior side debut on 6 March 2019, starting and playing the full 90 minutes of the Catalan Super Cup against Girona.[10] On 13 April 2019, he made his official debut in a La Liga match against Huesca where he played a full 90 minutes; he described it as a "dream come true".[11] Wagué again featured for the first team on 4 May 2019, impressing despite Barcelona's 0–2 defeat to Celta Vigo.[12] He would appear once more in Barcelona's La Liga finale, coming on as a second half substitute in a 2–2 draw with Eibar.
Wagué was officially promoted to the first team ahead of the 2019–20 season, and given the number 16 shirt.[13] He made his first Champions League start for Barcelona on 10 December 2019, as his side defeated Inter Milan 2–1.[14]
Loan to Nice
In 31 January 2020, French club OGC Nice confirmed a loan transfer for Wagué, keeping him until the end of the 2019–20 season, with an option to buy for €15,000,000.[15] He made his debut for Nice in their 2–1 victory over Lyon on 2 February 2020, coming on as a second half substitute.[16] On 7 March 2020, Wagué provided the winning assist in Nice's 2–1 derby victory against rivals AS Monaco.[17] Upon the cancellation of the Ligue 1 season due to the COVID-19 outbreak in France, he returned to Barcelona after Nice decided not to activate his purchase option.[18]
Loan to PAOK
On 21 September 2020, Barcelona confirmed the loan transfer of Wagué to Greek side PAOK on loan for the rest of the season.[19] On 13 December 2020, he suffered a severe knee injury during PAOK's local derby against Aris Thessaloniki. As a result he was slated to miss nine months of action.[20]
Gorica
On 18 July 2022, he joined Prva HNL club Gorica[21] On 9 December 2022, he was released from the club after having his contract mutually terminated.[22]
In June 2018, Wagué was named in Senegal's 23-man squad for the 2018 FIFA World Cup in Russia.[27] He became the youngest African goalscorer in World Cup history when he scored in Senegal's match against Japan at the age of just 19 years and 263 days.[28]
Wagué represented Senegal in the 2019 Africa Cup of Nations, which took place in Egypt. He participated in the first two group stage games and the semifinal match for a Senegal squad that reached the tournament final. [29]