Born in New York City to a Zimbabwean-born mother and English father, he was brought up in Essex and in Zimbabwe.
Fletcher was educated at Felsted School, an independent school in the village of Felsted (near Great Dunmow) in Essex, followed by King's College London, where he obtained a degree in Geography.
After training as a music producer, Fletcher began his journalism career in Cardiff, producing packages for BBC Radio Wales. He then moved to London to work behind the scenes at Radio 5 Live. Several years later he began working on BBC 2W, the digital TV channel for Wales. He also presented and reported on sport for BBC Wales Today.
From 2005 until 2011, Fletcher presented sports bulletins on the rolling news channel BBC News, and has also presented sport on the BBC Weekend News and BBC Breakfast on BBC One as well as BBC World News. In March 2010, Fletcher began reporting on news stories for BBC Breakfast.
In October 2011, Fletcher left the BBC to join Sky Sports News, where he worked until his departure in early 2014.
On 3 March 2014, it was announced Fletcher would become a sports newsreader on the new ITV Breakfast programme Good Morning Britain. He first appeared on the programme on its opening day, 28 April 2014.
In 2015, Fletcher presented Rebound, a ten-part daytime game show for ITV, airing in the 5 pm slot. A second series of the show was produced and aired in 2016. In September 2015, he appeared in an episode of All Star Mr & Mrs alongside his wife Luned.
Since October 2015, Fletcher has been an occasional reporter for Countryfile on BBC One.
Fletcher co-presented the BBC Two series Food Detectives alongside Tom Kerridge and Alice Roberts in 2016. Since 2017, he has presented the Sunday morning BBC One programme Sunday Morning Live alongside Emma Barnett.
Fletcher speaks fluent Welsh, and is married to Welsh television producer and director Luned Tonderai. The couple have two children; Lili and Reuben.
In 2014, Fletcher became a celebrity ambassador for the UK charity, Balls to Cancer. In September 2015, Sean became an ambassador for the Beating Bowel Cancer charity. He ran the 2015 and 2016 London Marathon to raise money for the charity. In 2017, Fletcher ran the London Marathon for Heads Together and Young Minds UK.
In 2016, he played for the 'Rest of the World' team on ITV's celebrity football match Soccer Aid, which supports UNICEF UK.TV
Ant & Dec's Saturday Night Takeaway (2015)
All Star Mr & Mrs (2015)