McDowell was born in Portrush, County Antrim, Northern Ireland, and played with Rathmore Golf Club since he was eight or nine years old.

[3] As a senior with the Blazers in 2002, McDowell won six of twelve college events and the Haskins Award, given to the outstanding collegiate golfer in the United States.

McDowell turned professional in 2002, and won that season's Volvo Scandinavian Masters, which was only his fourth start on the European Tour.

McDowell was not yet a full member of the PGA Tour, but his top-50 placing in the Official World Golf Ranking ensured that he received invitations to play in many events in the United States.

In 2008, McDowell returned to the winner's enclosure by winning first the Ballantine's Championship in South Korea, and then the Barclays Scottish Open.

He played in the 2008 Ryder Cup, earning 2.5 points for the European team and finished the season ranked fifth on the Order of Merit.

[10] There were celebrations in his native Portrush as well when news of McDowell's win broke,[2] with "the mother of all parties" planned to get underway in the town.

[6] The Daily Telegraph's Mark Reason opined: "The previous three tournaments in the United States have been won by Lee Westwood, Justin Rose [both English] and now McDowell.

[13] McDowell finished the 2010 season with another win at the Andalucía Valderrama Masters and was second behind Martin Kaymer in the 2010 Race to Dubai standings.

In May 2011, McDowell was in contention to win the PGA Tour's flagship event, The Players Championship, but shot a final round 79 to end his chances.

McDowell opened up the year with a third-place finish at the Abu Dhabi HSBC Golf Championship on the European Tour in January.

McDowell was runner up in May 2012 at the Volvo World Match Play Championship at the Finca Cortesin Golf Club, losing the final 1 down to Belgium's Nicolas Colsaerts.

Previously in the knockout stages, McDowell had beaten Richard Finch 3&2, Sergio García on the 19th hole and Rafa Cabrera-Bello 2 up.

After a good drive and approach to the green, he was faced with a 25-foot putt to tie the lead and force a playoff, but narrowly missed it to the left and had to settle for a par.

The following month, at the 2012 Open Championship at Royal Lytham & St Annes, McDowell was in contention on Sunday for the second consecutive major.

He had shot rounds of 67-69-67 during the first three days to be at seven under par and trail leader Adam Scott by four strokes in second place with Brandt Snedeker.

His challenge was ended at the par five 11th, when he snap hooked his second shot into the trees left and had to take a penalty drop, costing him a bogey.

It was his best ever showing at the tournament, beating Pádraig Harrington 2-up, Alex Norén in 20 holes and Shane Lowry 3&2, before losing 1-down to Jason Day in the quarter-finals.

In July 2013, he won the Alstom Open de France, shooting a final round of 67 to finish four shots ahead of Richard Sterne.

[21] In his next event, Alstom Open de France, he recorded his only win of the season, defending the title he won in 2013 despite going into the final round 8 shots behind Kevin Stadler.

[26] McDowell qualified to represent Europe at the 2014 Ryder Cup narrowly edging Stephen Gallacher for the final place based on Official World Golf Ranking points.

[27] At the Ryder Cup, he formed a successful partnership with former opponent Victor Dubuisson with comfortable wins the afternoon foursomes on Friday[28] and Saturday.

McDowell subsequently competed in the Race to Dubai Final Series events on the European Tour including a tie for third in the HSBC Champions.

[34] On 31 March 2019, McDowell won his fourth PGA Tour title at the Corales Puntacana Resort and Club Championship in the Dominican Republic.

In August, McDowell was suspended by LIV Golf for one tournament and fined US$125,000 for violating the circuit's anti-doping policy after using an over-the-counter decongestant medicine that included the banned substance R-methamphetamine.

[42] As he won the U.S. Open in 2010 he was living in a "bachelor pad" penthouse apartment in Portrush and was building a home in Lake Nona, Florida, United States.

[4] McDowell hired interior designer Kristin Stape to work on his Lake Nona house: subsequently the pair began dating and were engaged in October 2012.

In the buildup to the 2011 Masters Tournament he skipped the annual par-3 contest in order to watch a UEFA Champions League clash between United and Chelsea.

[52] He received his honorary degree from the University's Chancellor, the actor James Nesbitt on its Coleraine campus and in his speech to graduates, urged them to set their goals high in their careers and trust their intuition.

1Cancelled due to COVID-19 pandemic WD = Withdrew QF, R16, R32, R64 = Round in which player lost in match play NT = no tournament "T" = tied Note that the HSBC Champions did not become a WGC event until 2009.