Prior to the existence of official continental football in South America, Atlético Mineiro had played against foreign clubs since 1929, and toured Europe in 1950.
Goalkeeper Victor is the player with the most appearances in international competitions for the club, with 41; forwards Guilherme and Jô are Atlético's top goalscorers with 11 goals.
Before this official tournament, Chilean club Colo-Colo's President Robinson Alvarez had the idea for a South American Championship of Champions, which was eventually held in Santiago in 1948.
In 1958, the new CONMEBOL president, José Ramos de Freitas, contacted South American football associations intending to introduce an annual competition for clubs on the continent.
[4] From 1959 to 1968 the champions and runners-up of the Taça Brasil were the Brazilian representatives in the Copa Libertadores; the national competition had been created with the purpose of selecting the country's entrants in the continental tournament.
[5] Brazilian clubs did not enter the 1966, 1969 or 1970 editions of the competition, and in 1971 the champion and runner-up of the Torneio Roberto Gomes Pedrosa filled Brazil's berths.
After a 2–0 home win with a brace by Negrini at the Mineirão, and a 1–0 away defeat at the Defensores del Chaco, Atlético won its first official international trophy.
[10] In the Copa de Oro, Atlético faced its biggest rivals Cruzeiro in the semi-final, played as a single match at the Mineirão, the home stadium for both clubs, in front of a crowd of both teams' fans.
[32] In the Copa CONMEBOL, Atlético again eliminated Fluminense in the first round (this time in a penalty shootout), and defeated Peru's Sipesa in the quarter-finals with an aggregate score of 2–1.
[33]Absent from continental football for one season, Atlético Mineiro returned to the Copa CONMEBOL in the 1995 edition, qualifying after finishing fourth in the 1994 Brasileiro.
[35] In its second Copa CONMEBOL final, Atlético faced Argentine side Rosario Central, and secured a significant advantage in the series with a 4–0 win at the Mineirão.
In the semi-finals, Atlético faced Rosario Central for a third time in continental football, and was eliminated after a 1–1 draw at the Gigante de Arroyito and a 1–0 defeat at home.
The latter was a new continental competition introduced in 1998, which eventually replaced both the Copa CONMEBOL and the Supercopa Libertadores for clubs in Brazil, Argentina, Paraguay, and Uruguay.
In its return to the Copa Libertadores after nineteen years, Atlético was drawn in Group 8, with Bolivian Club Bolívar, Uruguayan side Bella Vista, and Chile's Cobreloa.
[43] In the Copa Mercosur, Atlético was drawn into Group E, with fellow Brazilian club Vasco da Gama, Uruguay's Peñarol and San Lorenzo from Argentina.
[47] Following its return to the Série A in 2007, the team finished eighth in the league and earned a spot in the following year's Copa Sudamericana,[48] but was eliminated in the first stage, after losing 8–3 on aggregate against Botafogo.
[50] After finishing in seventh place in the 2009 Série A, Atlético qualified for the 2010 Copa Sudamericana,[51] and advanced from the second preliminary stage by eliminating Grêmio Prudente after drawing 0–0 and winning 1–0.
[54] The team entered the competition in the second stage, and was drawn into Group 3, together with Argentine club Arsenal de Sarandí, Bolivia's The Strongest, and São Paulo once again.
With a squad composed of Ronaldinho, Jô, Diego Tardelli, Bernard and a returning Gilberto Silva, Atlético dominated the group, winning its first five matches.
São Paulo inflicted the team's only loss in the last match, but Atlético had already secured the best performance of the competition's group stage, which meant the second legs in further rounds would be played at home.
[59] In the finals, Atlético faced Olimpia for the second time in a continental decision, and the Paraguayan club won the first leg, played at the Defensores del Chaco, by 2–0.
[60] A Jô goal in the beginning of the second half, and a header by Leonardo Silva at the 87th minute, equalised the aggregate, and the match ended with the same score after extra-time.
[64] As winner of South America's main continental tournament, Atlético won the right to play in the 2013 FIFA Club World Cup in Morocco, its first official intercontinental competition.
After the unexpected defeat, the team faced the Chinese club, and Asian champion, Guangzhou Evergrande in the third place match, which it won 3–2 with an injury time goal.
Atlético qualified for the following stage in second place, and was eliminated in the round of 16 by Brazilian club Internacional, with a 2–2 draw in the first leg in Belo Horizonte and a 3–1 loss in Porto Alegre.
[71] Through its position in a new Copa Libertadores ranking introduced by CONMEBOL,[72][73] Atlético was seeded in Pot 1 for the 2016 edition, and joined in Group 5 by Colo-Colo, Peruvian champions Melgar, and Ecuador's Independiente del Valle.
In 2021, Atlético returns to Libertadores, where it fell in group H, alongside Cerro Porteño, América de Cali and Deportivo La Guaira.
In the first game of the Round of 16, away from home, they reached a draw against Emelec from Ecuador, but on the way back, the Galo won 1–0, with a penalty goal from striker Hulk and qualified for the Quarter-finals.
In his debut in the 2023 Copa Libertadores edition, Atlético Mineiro drew 0–0 away from home with Carabobo and in the return game, they advanced to the third phase by beating them 3–1.
In the semi-finals, they eliminated River Plate on aggregate 3–0, after a home win by the same score and a 0–0 draw in the return leg, thus securing qualification for their second Libertadores final in history.