The son of former Brazilian professional footballer Marcos Pereira, Andreas Pereira was born in Duffel, Belgium, while his father was a player there. He joined PSV Eindhoven in 2005, when he was nine years old. In 2011, after impressing at the Manchester United Premier Cup, he became a target for several big English clubs, including Arsenal, Chelsea and Liverpool, but a visit from Manchester United manager Alex Ferguson in November 2011 convinced Pereira to sign for the Old Trafford club.

Due to regulations regarding international transfers, the move could not be completed until Pereira’s 16th birthday on 1 January 2012, and further complications with international clearance meant that his Manchester United debut was delayed until April 2012. He made his debut for the under-18s in a league match away to Sheffield Wednesday on 25 April 2012, but heavy rain meant the match had to be abandoned as a goalless draw after 35 minutes. He made two more appearances that season as the under-18s finished eighth out of 10 teams in their Premier Academy League group.

After signing as an academy scholar in July 2012, Pereira became a regular in the under-18s in the 2012–13 season, making 20 appearances and scoring five goals. He also got his first taste of reserve team football during the season, coming on as a substitute for James Weir in a 3–1 win over Oldham Athletic in the Manchester Senior Cup, followed by another substitute appearance against Liverpool in the semi-finals of the Professional Development League. In recognition of his performances, on 7 January 2013, shortly after his 17th birthday, Pereira received his first professional contract. Ahead of the 2013–14 season, Pereira was named as Manchester United’s captain for their 2013 Milk Cup campaign, and was named Player of the Tournament for his three goals as Manchester United won the Premier Section. He went on to feature heavily for both the under-18s and the under-21s, and was ever present in the inaugural UEFA Youth League; he also scored twice in three appearances in the FA Youth Cup, including a curling, 25-yard effort against Burnley in the third round. For the under-21s, he appeared in 17 out of 21 league matches as Manchester United finished third; he then scored the only goal in the semi-final against Liverpool, only for the team to lose to Chelsea in the final.

Pereira began the 2014–15 season with silverware as Manchester United beat Manchester City 4–1 in the final of the Manchester Senior Cup on 7 August 2014. He made his senior debut three weeks later, coming on as a half-time substitute for Saidy Janko in a 4–0 away defeat to Milton Keynes Dons in the second round of the League Cup. On 15 March 2015, Pereira made his Premier League debut against Tottenham Hotspur, coming on as a 77th-minute substitute for Juan Mata in a 3–0 win for United.

Born in Belgium to a Brazilian father and a mother of German descent, Pereira is eligible to represent either Belgium or Brazil at international level. He initially represented Belgium at under-17 and under-18 level, but has since stated, “My heart is Brazilian.” He received his first Brazil call-up in 2014, joining the under-20s on their successful Panda Cup campaign in China.

On 21 July, Pereira scored his first goal for Manchester United’s senior squad in the 3–1 win against the San Jose Earthquakes in the 2015 International Champions Cup, after coming on as a second-half substitute. He made his first competitive start for the senior team on 23 September 2015, in the third round of the League Cup, and scored a free kick in the eventual 3–0 win over Ipswich Town.

At the 2015 FIFA U-20 World Cup in New Zealand, Pereira equalised in the final against Serbia, but Brazil lost 2–1 after extra time.

On 26 August 2016, Pereira joined Spanish club Granada on a season-long loan deal. He made his debut in La Liga two days later, replacing Luís Martins in the 55th minute of a 5–1 loss at UD Las Palmas.

Pereira scored his first goal for the Nazaríes on 3 December, opening a 2–1 home win over fellow Andalusians Sevilla FC. On 6 February 2017, he netted the only goal of a win over Las Palmas at the Estadio Nuevo Los Cármenes, with a long-range strike. Eleven days later, he was again on the scoresheet for a 4–1 victory against Real Betis at the same ground, but was sent off for a push; he was banned for two games and the club fined €180.

On 1 September 2017, Valencia announced the arrival of Pereira to the club on a season-long loan deal. He made his debut in a 0–0 home draw against Atlético Madrid eight days later, and scored his only goal for Los Che on 15 October, with a long-range strike as a substitute to conclude a 6–3 win at Real Betis.

On 17 August 2018, he received his first senior call up for the friendly matches against United States and El Salvador. He made his debut against El Salvador on 11 September, as the first player in over 100 years to play for Brazil having been born outside of the country.

On 2 March 2019, Pereira scored his first Premier League goal in a home match against Southampton. The goal later earned him Manchester United’s goal of the season for 2018-19 season. He also recorded an assist for Romelu Lukaku in the same match. On 7 March 2019, Pereira was featured in the starting lineup during the historic Champions League Round of 16 (2nd Leg) win vs PSG, where the team was able to come back from a 2-goal deficit they conceded at home and win on away goals at the Parc des Princes, a record that has never been broken before.

On 11 August 2019, Pereira started in Manchester United’s opening day 4–0 win against Chelsea, in which he assisted Anthony Martial for the second goal. On 10 November 2019, Pereira scored his first goal of the season in a 3–1 home win against Brighton.

On 2 October 2020, Lazio announced the arrival of Pereira to the club on a season-long loan.