Bentancur is a product of the Boca Juniors youth academy. On 12 April 2015, he made his first team debut for the club in a league game against Nueva Chicago. He replaced Pablo Pérez after 77 minutes in a 0–0 home draw.

On 13 July 2015, Bentancur, Guido Vadalá, Franco Cristaldo and Adrián Cubas became part of Carlos Tevez’s deal, which saw Juventus have the first option to sign the youngsters until 20 April 2017, with Vadalá also joining Juventus on loan for the 2015–2017 seasons. Bentancur was tagged for €9.4 million. Juventus’s CEO Giuseppe Marotta later confirmed that Juventus would be exercising their option to sign Bentancur in 2017. He arrived in Turin on 3 April 2017 and completed his medical on the same day. On 21 April 2017 Juventus completed their acquisition of Bentancur, signing him on a five-year deal effective from 1 July 2017 until 30 June 2022 for a €9.5 million transfer fee, plus additional performance based bonuses. Boca Juniors are also entitled to 50% of any future transfer fee that Juventus receive for Bentancur. Bentancur subsequently returned to Argentina to play out the remainder of the 2016–17 season with Boca Juniors.

Bentancur formally became a player of Juventus on 1 July 2017, after the club activated the option to sign him in April 2017, in a deal which would keep him at the club until 2022. The first option to sign Bentancur was bought as part of Carlos Tevez’s deal in July 2015. He made his club debut on 26 August 2017, coming on as a substitute in a 4–2 away win over Genoa in Serie A.

Bentancur was a member of Uruguayan national under-20 team, winning 2017 South American U-20 Championship. The squad also finished as the fourth in 2017 FIFA U-20 World Cup.

In September 2017, Bentancur received his first senior call-up to the Uruguayan national team by manager Óscar Tabárez for the team’s upcoming 2018 World Cup qualifiers against Venezuela and Bolivia in October. He made his international debut on 5 October, coming on as a substitute in Uruguay’s 0–0 away draw against Venezuela. He was named in the squad for the China Cup in March 2018.

On 6 October 2018, Bentancur scored his first goal for the club in a 2–0 away win over Udinese in Serie A.

In May 2018, Bentancur was named in Uruguay’s provisional 26-man squad for the 2018 FIFA World Cup in Russia. He was later included in the team’s final 23-man squad for the tournament. He appeared in Uruguay’s opening match of the tournament on 15 June, a 1–0 victory over Egypt at the Yekaterinburg Arena. In the Round of 16 match against Portugal on 30 June, he set-up Edinson Cavani’s second goal in an eventual 2–1 victory. Uruguay were eliminated from the tournament following a 2–0 defeat to eventual champions France in the quarter-finals on 6 July.

In March 2019, Tabárez included Bentancur in the final 23-man Uruguay squad for the 2019 Copa América in Brazil. In the quarter-finals against Peru on 29 June, a 0–0 draw after regulation time saw the match go to a penalty shoot-out; although Bentancur was able to score his kick, Uruguay lost the shoot-out 4–5 and were eliminated from the competition.