She wrote: "Not something I ever wanted to write but here we go.
"Daley, as Daisy says, is now sleeping with the fairies. That's all I can bring myself to say right now.
"The last image I saw of my husband, was of a man so happy with life and so proud of his racing."
Penz13.com BMW rider Mathison was competing in his sixth Isle of Man TT after making his debut in 2014.
He finished second in the Zero Race in 2018 and third in both 2016 and 2017.
The tributes flooded in on social media once the shocking news broke - with legendary motorbiker Carl Fogarty one of the first to post.
The 53-year-old wrote: "Sad to hear of the death of Daley Mathison in today's TT superbike race.
"Thoughts are with family and friends."
The race he was competing in was immediately red-flagged, with the result being declared on the lap two times.
Race organisers the ACU released a lengthy statement that read: "ACU Events Ltd regrets to confirm that Daley Mathison, 27, from Stockton on Tees, Durham was killed in an incident during the Superbike race today at the Isle of Man TT Races.
"The accident occurred at Snugborough, just over two miles into the course, on the third lap of the race.
"Daley was an experienced competitor and was seeded 19th for today's race.
"ACU Events Ltd wishes to pass on their deepest sympathy to Daley's wife Natalie, his family and friends."
Mathison started racing at the age of 12, according to the North East Echo, and had helped students in his native North East with their motor racing ambitions.
Last year two racers lost their lives in the Isle of Man TT.
Local man Dan Kneen lost his life in the Superbike TT qualifying and Adam Lyon was killed during the Monster Energy Supersport 1 race.
There was also one death in the classic race, 62-year-old Alan "Bud" Johnson crashed out and died in a practice session.
He was a 30-year veteran of the world famous road race.
In total 258 riders have been killed at the event since it began back in 1911.
