Mancini started his career at Inter Milan where his father was the first team coach. He started as a member of the Giovanissimi Regionali team in the 2005–06 season, and had moved up to the Allievi Regionali team for the 2007–08 season. The next season (2008–09), he left Inter for a loan spell with the Monza youth team, along with a number of other young Inter players that included his elder brother, Filippo. He was released from Inter as a free agent in June 2009.
Mancini was signed up by the Manchester City 'Under-21' youth team in November 2010 after he was released by his former club Bologna in Italy. He scored 3 goals for Bologna reserve.
On 3 November 2011, Mancini started a one-month loan spell at Oldham Athletic along with his Elite Development Squad teammate Luca Scapuzzi. He made his debut two days later as a late substitute in the Latics' home defeat to local rivals Bury and was also an 85th-minute substitute for the home side in the Football League Trophy quarter-final game against Crewe Alexandra three days later. Mancini extended his loan for a further month despite only appearing twice as a substitute so far. Andrea Mancini was sent back to his parent club after a disappointing loan spell, only making two substitute appearances in two months for the club.
After spells at Fano and Oldham Athletic on loan, Andrea returned to Manchester City. On 25 May 2012 Manchester City released Andrea. Andrea only spent a year at the English club making no senior appearances. Mancini was on trial with League One side Bournemouth during the 2012/13 pre-season.
On 27 July 2012 Andrea signed a 1-year contract with Spanish club Real Valladolid B.
On 19 June 2013, Mancini was signed by Hungarian League club Budapest Honvéd. On 12 July 2013, Roberto Mancini watched his son live playing in the UEFA Europa League 2013–14 season against Čelik Nikšić. The match ended with a 9-0 victory for Budapest Honvéd.
On 29 October 2014, Mancini terminated his contract with Budapest Honvéd.
During his period in Budapest, Mancini played 23 matches and scored 2 goals. He made 11 appearances in the Hungarian League.
On 20 January 2015, Mancini was signed by Hungarian League club Szombathely.
On 5 March 2016, Mancini signed with D.C. United of Major League Soccer.
On September 9, 2016, Mancini signed with New York Cosmos of North American Soccer League.
Updated to games played as of 7 March 2016.