D P World Tour Championship 2013. Watercolour sketch
Manassero turned pro on 3 May 2010, making his professional debut at the BMW Italian Open. His first win came on 24 October 2010 at the Castelló Masters Costa Azahar in Valencia, Spain, where he triumphed by four strokes over Ignacio Garrido. The victory made him the youngest ever winner on the European Tour, surpassing the record set by Danny Lee at the 2009 Johnnie Walker Classic. The victory also secured his full European Tour playing privileges for the next two seasons. Manassero posted another very strong result when he tied for second in the 2010 UBS Hong Kong Open, one stroke behind winner Ian Poulter. He won the Sir Henry Cotton Rookie of the Year in 2010. In 2011 Manassero secured his second European Tour win at the Maybank Malaysian Open on 17 April 2011 at the age of 17 years and 363 days, making him first and second on the list of youngest European Tour winners. In 2012 he managed to further improve his results: in November 2012, after a win at the Barclays Singapore Open, he became the first teenager to win three times on the European Tour. He also collected a second place at the Open de Andalucía Costa del Sol, and five more top 10 placements that earned him the 13th place in the final Order of Merit. In 2013, Manassero won the biggest tournament of his career to date: the 2013 BMW PGA Championship with a birdie at the fourth extra hole of a playoff against Simon Khan and Marc Warren, becoming the youngest ever winner of this tournament. With the win Manassero gained the right to play in the 2013 U.S. Open and entered the top 30 of the Official World Golf Ranking. He also managed to further improve his final Order of Merit position with an 11th place. After collecting a 4th place at the 2014 Aberdeen Asset Management Scottish Open as the sole top 10 result of the season, 2015 proved to be a more difficult year for Manassero in the European Tour, where he was able to make only 6 cuts in 22 competitions. He finished 167th in the final Order of Merit, but was able to retain his tour membership in virtue of the win at the 2013 BMW PGA Championship. After the first round of the 2016 Scottish Open, Manassero opened up to bunkered magazine about "deep lows" he had suffered during his period of struggle. He went on to finish T3 at Castle Stuart, his best result on the European Tour all season. Manassero won his first professional event in seven years at the 2020 Toscana Open on the Alps Tour, two tiers below the European Tour.