Boselli made his debut for Boca Juniors in a 7-2 defeat to Rosario Central on July 6, 2003, for the last fixture of the 2003 Clausura. He subsequently spent the 2005–06 season on loan at Málaga B in the Spanish Segunda División. After returning to Boca Juniors, Boselli struggled to become a regular in the first team, being behind Martín Palermo and Argentina World Cup player Rodrigo Palacio in the coaches' consideration.
In July 2008, Estudiantes de La Plata bought 50% of Boselli's transfer rights from Boca, allowing the forward to move to the La Plata outfit. In Estudiantes, Boselli started strongly with 8 goals in 15 league games during his first tournament, the 2008 Apertura. In 2009, he won the Copa Libertadores with Estudiantes. During the competition, Boselli scored 8 goals, finishing as the overall top scorer of the tournament. He also helped the team by scoring the winning goal in the tournament's final against Cruzeiro, in Belo Horizonte. In total, Mauro Boselli scored 49 goals at Estudiantes de la Plata since June 2008. He hit 32 goals in the Argentine Primera División and a further 17 goals in international cups: 12 in the Copa Libertadores, four in the Copa Sudamericana and one in the FIFA Club World Cup.
On 29 June 2010, Boselli signed a four-year deal with Wigan Athletic for an undisclosed fee, believed to be around £6.5 million. He made his debut in the opening game of the Premier League season against Blackpool, and scored his first competitive goal for the club against Swansea City in the League Cup on 26 October 2010. However, following his first goal for the club, Boselli has found settling into the English Premier League difficult.
Mauro Boselli was loaned to Italian Serie A side Genoa for the remainder of the 2010-2011 season. He had 2 goals for Genoa.
Boselli was loaned out to Estudiantes in Argentina. Mauro returns his former team for the season.
In 2005, Boselli was part of the Argentine U-20 national team that finished third in the South American Youth Championship (therefore qulifying for that year's U-20 World Cup). However, Boselli was not part of the final World Cup squad.
On September 27, 2009, Boselli was called for a local-league based Argentine national team (replacing injured Esteban Fuertes) to play a friendly match against Ghana. Three days later, on 30 September, Boselli debuted with the national team, being brought in as a substitute in the 57th minute of the match. Boselli scored his first goal for Argentina- from the penalty spot- in a 4-1 defeat to Nigeria on June 1, 2011.
2003–2008 Boca Juniors 44 appearances - 10 goals
2005–2006 → Málaga B (loan) 32 appearances - 5 goals
2008–2010 Estudiantes 56 appearances - 32 goals
2010– Wigan Athletic 8 appearances
2011 → Genoa (loan) 7 appearances - 2 goals
2011- → Estudiantes (loan) 13 appeances - 3 goals
2004 Boca Juniors - Copa Sudamericana
2007 Boca Juniors - Copa Libertadores
2009 Estudiantes - Copa Libertadores
2009 Estudiantes - Copa Libertadores top scorer
2010 Estudiantes - A.F.A. Clausura Top Scorer
Amazing scorer emerged from lower divisions of Boca Juniors, but another missed centreforward because of Palermo's legend. He suffered this some years and decided to go to Estudiantes...there he showed the best of himself. Timing, being a real poacher, excellent positioning in and out of the box, intelligent movements to avoid markers and fire in his shoots. He was a really good placer of the ball, with refined technique of shoot and good header shot. It's remembered his goal vs Barcelona, heading between Abidal and other Barsa defender to dream with the title. He hadn't luck in England and Italy, and not too many opportunities, so he decided to return to play in Estudiantes, which hadn't a good tournament currently. Just went with Konami values in some stats as they are really good...kinda strange some of them but basically correct, I don't agree at all with so low attack in 77 that they gave, it's just wrong. He was an awesome positional sense in those times and it's true that he relied a lot in his resp/st combo, he knew how to move and be a nightmare to defences.