More than 100 Manx runners will wear a red bow while competing in the London Marathon, in memory of Murray Lambden who died last week.
The 60-year-old died suddenly on 17 April, collapsing while walking his dog on the Isle of Man.
Mr Lambden represented the island at the 1982 Commonwealth Games and had a personal best at the London Marathon of two hours 43 minutes.
He has been descried as a "true ambassador for Manx athletics".
A spokesman for the Manx Harriers Athletics Club said he was "not only a fabulous athlete but... a giant of Manx athletics".
His sister Margaid Gosschalk is planning to stand with a Manx flag at the five-mile point, where he would have been standing to cheer his fellow athletes on.
She said: "As he won't be there, we have ordered a Manx flag and I will be there. It's the least we can do in Murray's memory.
"He was proud to represent both the Isle of Man and GB and the incredible tributes I have been reading on so many sites from athletes and friends shows just how much people appreciated all he did to support and encourage others."
The married father of two's achievements included winning the 85-mile Parish Walk.
In recent years he was an ever-present at sporting events with his camera and administered the Parish Walk website.