The 26-year-old was reported missing from Purley, South London, last October, prompting an appeal for information from his former mentor.
A body was found in the back garden of a house in Coulsdon, south London, on Sunday afternoon. His death is being treated as unexplained, with a post-mortem examination planned to take place in Croydon on Tuesday.
"I'm deeply saddened by this tragic news,” said TV chef Oliver. “I’m proud to have been able to call Kevin a friend for 10 years.
"He was also a constant supporter of Fifteen and all the apprentices and graduates who came after him through the course. I last saw him in September 2011 at the graduation ceremony for the ninth group of apprentices and he was on good form, which makes this news even harder to take.
"My thoughts are with his family at this incredibly difficult time."
Jamie Oliver’s Fifteen
Boyle featured on Oliver's TV programme Fifteen in 2002 where he made it to the final 30 of 1,500 people. He also cooked for former Prime Minister Tony Blair and Prince Charles at Clarence House.
In a Twitter campaign to try and find him, fellow chef Delia Smith, TV presenter Sue Perkins, magician Chris Cox, the Salvation Army and Crystal Palace football club all joined in to support.
Peter Fosdike posted a message on the website set up to find Boyle on behalf of his friends at Purley Baptist Church.
The message reads: “Kevin never failed to amaze us or make an impact on our lives. He was passionate about his friends and we are only now seeing just how many friends from all over the world he has, he was truly and deeply loved by so many.
“He used to cook for his friends and surprise them with tastes that we may never have the delight of experiencing again, he was a masterful chef.
“Our deepest condolences to the Boyle Family; on behalf of Kevin's friends at Purley Baptist Church.”
A Scotland Yard spokesman said: "The death is being treated as unexplained at this stage. A post mortem will be arranged in due course."
In 2008, Christopher Pethick - one of the first trainees to sign up to Jamie Oliver's chef training scheme at Fifteen in Cornwall - was discovered hanging in woodland not far from the famous restaurant.