Born in Novo Hamburgo, Rio Grande do Sul,^[4]Alisson joined Internacional's academy in 2002, aged ten.^[2][5] Having progressed through the youth set up, he featured regularly with the under-23 side, before making his senior debut on 17 February 2013, starting in a 1–1 away draw against Cruzeiro-RS in the Campeonato Gaúchochampionship.^[6] His Série A debut followed on 25 August 2013 when he started in a 3–3 home draw against Goiás.^[7] A backup to his brother Murieland competing for second-choice with Agenor, he finished his first season with six appearances.^[2]

The following year, Alisson found himself competing with Brazilian legend Dida, who had joined Internacional from Grêmio. He earned a starting berth in October and finished the yearwith 11 league appearances to his name.^[8] He was an undisputed starter in the following yearduring which he amassed 57 appearances across all competitions. On 4 February 2016, Alisson signed a pre-contract with Italian club Roma, signing a five-year deal for a €7.5 million fee.^[9] He played his last game for Internacional on 15 May 2016, keeping a clean sheet in a 0–0 home draw against Chapecoense.^[10] During his four years with Internacional's senior side, Alisson made over 100 appearances across all competitions and won the Campeonato Gaúcho title in each season.^[2]

Alisson completed his transfer to Italian Serie Aclub Roma in July 2016.^[11] He made his debut for the club on 17 August 2016, starting in a 1–1 UEFA Champions League draw with Porto, but spent the majority of the season as understudy to Wojciech Szczęsny.^[12] He ultimately made 15 appearances across all competitions from the season but failed to feature in any league fixtures. Szczęsny departed at the start of the following campaign for Juventus, which saw Alisson assume the number one jersey. He later revealed that he would have considered leaving Roma had he not been guaranteed more first-team football.^[13]

Alisson finally made his Serie A debut on the opening weekend of the 2017–18 Serie Acampaign, starting in a 1–0 win over Atalanta.^[14]He then made his first appearance in the Derby della Capitale on 18 November, starting in a 2–1 win over local rivals Lazio.^[15] He was praised for his performances in the 2017–18 Champions League, and played a key role in the club's campaign in which they reached the semi-finals.^[16][17] The club didn't concede a single goal at the Stadio Olimpico in the Champions League, until the match against Liverpool in the semi-finals on 2 May 2018, which they won 4–2 on the night, but lost 7–6 on aggregate.^[18] Alisson received praise for his performances throughout the 2017–18 season.^[19] He kept a total of 22 clean sheets across the 2017–18 season, keeping 17 clean sheets in the league and 5 clean sheets in the Champions League.^[20][21]

On 19 July 2018, Liverpool confirmed the signing of Alisson for a fee of £66.8 million (€72.5 million), making him the most expensive goalkeeper of all time.^{[22][23][24][25]} However, the fee was broken just four weeks later when Chelsea signed Kepa Arrizabalaga for a reported £71.6 million (€80 million).^[26] On 10 August, Liverpool confirmed via their official website that he would wear the vacant number 13 shirt in the 2018–19 season.^[27]

Alisson made his debut for Liverpool on 12 August, keeping a clean sheet in a 4–0 win over West Ham United.^[28] He received praise for his subsequent performances in wins over Crystal Palace and Brighton which saw him keep three consecutive clean sheets.^[29][30] In August, Alisson was shortlisted for Champions League Goalkeeper of the Season,^[31] finishing in second place.^[32] However, with Alisson in goal, Liverpool went on a run of 20 games unbeaten in the league from the start of the season which saw the Brazilian break Javier Mascherano's record for the longest-such streak.^[33] Alisson also played an important role in Liverpool's Champions League group stage campaign, making a vital save late on in their final group game against Napoli as Liverpool won 1–0 to advance to the knockout stages.^[34]

On 4 March 2019, he kept his 17th Premier League clean sheet for the season; the most by any Premier League goalkeeper in his debut season since former Liverpool goalkeeper, Pepe Reina in 2006.^[35] At the end of the season, Alisson kept a total of 21 clean sheets in Premier League, and won the Golden Glove.^[36] In the Champions League knockout stages, meanwhile, Alisson played a starring role as Liverpool advanced to their second consecutive final in the competition; in their second-leg semi-final at home to Barcelona, he made a number of impressive saves as Liverpool overturned a 3–0 first leg deficit to advance past their opponents with a 4–0 home win.^[37] In the final on 1 June 2019, Alisson kept a clean sheet for Liverpool as they defeated Tottenham Hotspur 2–0, making eight saves in the process, to win his first trophy with the club.^[38]

After spending his first season with the designated squad number 13, it was announced that Alisson would be wearing the number 1 shirt for the 2019–20 season, which had previously been worn by Loris Karius.^[39][40]

Alisson started in the 2019 FA Community Shieldagainst Manchester City on 4 August; after a 1–1 draw, Manchester City ultimately won the title 5–4 on penalties.^[41] On 9 August 2019, in the opening match of the 2019–20 Premier League season against newly promoted Norwich at Anfield, Alisson picked up a calf injury in the first half, and had to be replaced by new signing Adrián after 38 minutes.^[42] He was expected to be out injured for a "few weeks".^[43] As a result, he was ruled out of the 2019 UEFA Super Cup,^[44] which Liverpool won 5–4 on penalties on 14 August, following a 2–2 draw with Chelsea after extra-time.^[45] He returned to the matchday squad on 20 October, in a 1–1 draw with rivals Manchester United.^[46] On 30 November, in a 2–1 win over Brighton, he was sent off for handling the ball outside his designated area.^[47] On 21 December, Alisson kept a clean sheet against Flamengo in the 2019 FIFA Club World Cup final with Liverpool winning the trophy for the first time.^[48] On 19 January 2020, Alisson assisted Mohamed Salah's 93rd-minute goal, in a 2–0 home win against Manchester United in the league.^[49]

On 6 March 2020, Alisson was injured again,^[50]meaning he missed the next day's Premier League win against AFC Bournemouth, and the Champions League round of 16 second leg loss against Atlético Madrid, the final two Liverpool matches before the season was suspended due to the COVID-19 pandemic. He ended the 2019–20 Premier League with a Premier League winner's medal, having made 29 appearances.^[51]

On 20 September 2020, Alisson saved a penalty in Liverpool's second league game of the 2020–21 Premier League season, a 2–0 away win over Chelsea.^[52] This was Alisson's first penalty save for Liverpool since joining the club, and Jorginho's first missed penalty in nine attempts for Chelsea in all competitions.^[53] On 7 February 2021, Alisson made two errors in the space of three minutes, conceding possession to allow Manchester City's İlkay Gündoğan and Raheem Sterling to score, as Liverpool lost 4–1.^[54] On 16 May 2021, Alisson scored a dramatic late winner in a 2–1 victory against West Bromwich Albion. With Liverpool chasing a spot in the top four and the score tied at 1–1, Alisson came up for a Liverpool corner in the 95th minute. The corner, taken by Trent Alexander-Arnold, found Alisson, who managed to score with a header. This was the first goal scored by a keeper in a competitive match in Liverpool's 129-year history,^[55] and Alisson became the sixth goalkeeper to score in the Premier League.^[56]

On 4 August 2021, prior to the beginning of the 2021–22 Premier League season, Alisson signed a new contract extension to stay with Liverpool until the summer of 2027.^[57] On 15 May 2022, Alisson won the FA Cup with Liverpool, defeating rivals Chelsea 6–5 on penalties in the final. Alisson saved a penalty from Mason Mount, allowing Liverpool's Kostas Tsimikas to score the winning penalty in the shoot-out.^[58] Moreover, Alisson earned a runners-up medal in the Champions League as Liverpool lost 1–0 to Real Madrid in the final.^[59] Liverpool narrowly missed out on the chance to achieve a historic quadruple, coming second in the Premier League and the 2021–22 UEFA Champions League but winning both the EFL Cup and the FA Cup.^[60]

On 16 October 2022, Alisson assisted Mohamed Salah for a late winning goal in Liverpool's 1–0 win over rivals Manchester City in the Premier League. Alisson became the goalkeeper with the most goal contributions in Premier League history, with 3 assists and 1 goal for Liverpool.^[61] Three days later, on 19 October, Alisson saved a penalty from Jarrod Bowen as Liverpool beat West Ham United 1–0 in the Premier League.^[62] Alisson was named Liverpool's Player of the Month for October 2022.^[63] Alisson reached 100 clean sheets for Liverpool on 6 May 2023 in a 1–0 victory against Brentford.^[64] At the end of the 2022–23 season, Liverpool narrowly missed out on UEFA Champions League qualification.^[65] Despite this, Alisson was widely praised as one of the best performers in the Premier League that season.^[66]

On 27 August 2023, Alisson made an acrobatic save to deny Miguel Almirón from scoring in a 2–1 victory against Newcastle United which would later earn him the Premier League Save of the Month award for August.^[67] On October 5, 2024, he was injured during the team's match against Crystal Palace.^[68]