Nicknamed El Muñeco (the doll) due to his small frame (169 cm, 70 kg), Gallardo started his football career back in 1992-93 season with River Plate and won 4 Argentinian Torneo de Apertura (93, 94, 96 and 97), 1 Argentinian Torneo de Clausura (1997) and 1 Copa Libertadores (1996).
His initial spell with los millonarios lasted until season 1998-99; by then he had played 109 league games for them and scored 18 goals.
In 1999, he was snapped up by Monaco. In his first season in Europe, Gallardo proved his worth and played 28 games, scoring 8 goals and formed lethal partnership with Ludovic Giuly in Midfield.
In the following season, Gallardo won his first Première Division and Trophée Des Champions with Monaco. As a team containing many big-name players such as Marco Simone, Fabien Barthez, Willy Sagnol, Martin Djetou, Pablo Contreras, Ludovic Giuly, Philippe Christanval, Rafael Márquez, Sabri Lamouchi, David Trezeguet, and John Arne Riise, Monaco enjoyed their success domestically and it was evident Gallardo was one of the star players, having won the French League Footballer of the Year that year.
However, in his third season, things did not go well off the pitch for Gallardo as he was not in good terms with his coach Didier Deschamps after being named on the bench midway through 2000-01 season. Following the examples of Panucci and Simone, Gallardo decided to leave Monaco at the end of the season.
After making 102 appearances and scoring 18 goals for Monaco, Gallardo returned to his old club River Plate as club captain, he helped them win another Clausura in 2004.
Marcello Gallardo was bought by the Parisian club PSG for an undisclosed fee in January 2007. Paris Saint-Germain signed a two-year contract with Marcelo and made his debut in a 3-0 cup win against Nîmes on 7 January.
On 13 January 2007 he played his first Ligue 1 match for PSG against Valenciennes
After spending only one season with the club, Gallardo terminated his contract, looking to move to Major League Soccer in the United States.
On 29 January 2008 Gallardo was presented as the newest member of D.C. United. With a 2008 salary of $1.87 million, Gallardo is (still) the highest-paid player in United history and was its first Designated Player. Gallardo had the third-largest salary in MLS for 2008, behind English midfielder David Beckham of the Los Angeles Galaxy ($6.5 million guaranteed) and Mexican forward Cuauhtémoc Blanco of the Chicago Fire ($2.67 million). He scored his first league goal for United on 5 April 2008 against Toronto FC. On 17 and 19 July Gallardo underwent surgery for a sports hernia. In February 2009 he left D.C. United and returned for the third time to his old club River Plate.
In 2010, he signed at Nacional de Montevideo in the Uruguayan League. On 12 June 2011, Gallardo played his last match winning the Uruguay Tournament making him one of the few players to win a championship or a league in every team that he played. He retired as a player, and was hired a few days later as new manager of Nacional, his first job as a football manager.
Gallardo made his international debut for Argentina in 1994 against Chile and made 44 appearances and scored 13 goals.
He was also in the Argentina squad for the 1998 World Cup and 2002 World Cup.
He won the 2011/2012 championship and left the club. He was assisted by Matías Biscay, Pablo Rodríguez and professor Marcelo Tulbovitz during his time at Nacional Montevideo.
On June 6, 2014, Gallardo was presented as the new manager of River Plate following the controversial resign of Ramón Díaz on May 27. Key players from the previous tournament, Carlos Carbonero, Manuel Lanzini, and Cristian Ledesma left the club, while players relegated by Ramón Díaz such as Carlos Sánchez and Rodrigo Mora returned. River Plate only bought two players: an attacking midfielder, Leonardo Pisculichi (who had been relegated to second division with Argentinos Juniors) and goalkeeper Julio Chiarini (from Instituto de Córdoba).
Gallardo's style of play was widely lauded by the Argentine press, with the team matching the club's all-time unbeaten record on November 9 with 32 undefeated games, losing to Estudiantes de La Plata three days later. Out of the 32 games, 8 belonged to Ramón Díaz's tenure. River Plate led the Torneo de Transición for the better part, until Gallardo's team reached the Copa Sudamericana's semi-finals, where River would face rivals Boca Juniors. Planning to rest the players for the semi-finals, Gallardo played a substitute team against second-placed Racing Club, ultimately losing the match from an own goal by Ramiro Funes Mori. Racing would go on to win its first championship since 2001 by two points over River Plate.
River eliminated Boca with a lone goal from Leonardo Pisculichi in the second leg played at the Monumental. In the 2014 Copa Sudamericana Finals, Pisculichi scored once again to draw 1-1 against Atlético Nacional in the away leg at the Estadio Atanasio Girardot. Defenders Gabriel Mercado and Germán Pezzella, in the span of four minutes, scored with headers in the second leg at the Monumental, giving River Plate a 2-0 win and its first international title since 1997, remaining unbeaten in the competition. Marcelo Gallardo became the first River Plate player to win an international title both as a player and a coach. Following the end of the game, Gallardo dedicated the win to his mother, who had died shortly before the second game against Boca Juniors.
In early 2015, Gallardo's River won the Recopa Sudamericana 2015 against Copa Libertadores 2014 champions San Lorenzo de Almagro, by beating them 1-0 at home in the first leg, then once again 1-0 in the second leg, both goals scored by Carlos Sánchez. Later, on March, River won another international title, this time being the friendly 2015 Supercopa Euroamericana against 2013-14 UEFA Europa League champions Sevilla FC. The one legged match took place at the Monumental. River won 1-0 with a goal from Juan Cruz Kaprof.
After a deficient group stage that nearly got the team out of the tournament, Gallardo's River advanced to the 2015 Copa Libertadores Round of 16 as the worst second placed team from the group stage, having to once again face rivals Boca Juniors, the best first placed team. River won the first leg at home 1-0 with a penalty kick from Carlos Sánchez. In the second leg played at La Bombonera, the teams had completed the first half drawing 0-0. Upon returning to the pitch to play the second half, River Plate's players were attacked by Boca Juniors' fans. After an hour of recess, the match was suspended by a CONMEBOL official representative. Days later, the organization ruled to disqualify Boca Juniors, which resulted in River advancing to the tournament's quarter-finals.
Later on, the team reached the Libertadores final and played against Mexico's Tigres UANL. In the first leg at the Estadio Universitario, the game turned out scoreless. In the second leg played at the Monumental, River won 3-0 with goals from Lucas Alario, Carlos Sánchez and Ramiro Funes Mori.
The very next day, Gallardo's team travelled to Osaka, Japan, to play the 2015 Suruga Bank Championship against 2014 J. League Cup winners Gamba Osaka. The match resulted in a 3-0 victory for River Plate, with the team earning the 4th official international title under Gallardo's tenure.
Later that year, after a weak finish at the 2015 Argentine Primera División tournament, River advanced to the semi-finals of the 2015 Copa Sudamericana to play against fellow Argentines Club Atlético Huracán. The two legged series resulted in a 1-0 loss for River in the first leg played at home, then a 2-2 draw in the second leg. This would mark Gallardo's first defeat at an international knockout stage as a coach.
At the year's end, River played the 2015 FIFA Club World Cup, beating Sanfrecce Hiroshima 1-0 in the semi-finals with a goal from Lucas Alario. They would later lose the final against European champions Fútbol Club Barcelona by 3-0, with goals from Messi and Suárez (x2).
River Plate participated again in the 2016 Copa Libertadores as the defending champions. After advancing to the Round of 16, the team was eliminated by Independiente del Valle, who would later finish the tournament as runner-ups.
In mid 2016, Gallardo's River won the 2016 Recopa Sudamericana against 2015 Copa Sudamericana champions Independiente Santa Fe, by beating them 2-1 at home in the second leg after a scoreless first leg, adding yet another international title to his tenure as the team's coach.
Marcelo Gallardo remains as the most successful coach at an international stage in the club's history, with a total of five official international titles and one unofficial international friendly won.
Throughout his career, Gallardo tended to play in a central role as an advanced playmaker. A skilful player, who possessed an intelligent footballing brain, he was highly regarded for his ability to take on and beat opponents in one on one situations, although he was best known for his defence splitting passes. He was also well known for his accuracy from direct free kicks and his ball delivery from corners and set-pieces.River Plate
Primera División Argentina (6): 1993 Apertura, 1994 Apertura, 1996 Apertura, 1997 Apertura, 1997 Clausura, 2004 Clausura
Copa Libertadores: 1996
Supercopa Sudamericana: 1997
Division 1: 1999–2000
Trophée des champions: 2000
Coupe de la Ligue: 2003
Coupe de la Ligue: 2008
U.S. Open Cup: 2008
Uruguayan Primera División: 2010–11
Olympic Silver Medal: 1996
Pan American Games: 1995 Mar del Plata
Uruguayan Primera División: 2011–12
Copa Sudamericana: 2014
Recopa Sudamericana: 2015, 2016
Copa Libertadores: 2015
Supercopa Euroamericana: 2015
Suruga Bank Championship: 2015
Copa Argentina: 2015–16
Ligue 1 Player of the year: 2000