It was a complete surprise for Cain (81) when he collected the mail from the letter box at his Fairfield home last week.
There was a a certificate of gratitude and recognition from the IAAF to mark the celebration of its centenary this year.
"The letter arrived out of the blue," Cain said.
"I knew nothing about it at all. I don't think anyone did."
Cain was made a life member of Athletics New Zealand two years ago.
"That was nice," Cain said.
"But getting this recognition from the IAAF was special."
The other Otago administrator to receive the award from the IAAF was Raylene Bates, who was manager of the New Zealand track and field team at the London Olympics and head coach of the team at the Paralympics.
There were only 23 IAAF certificates awarded to New Zealand athletics officials and administrators.
Cain was a successful distance runner and represented Otago at the New Zealand cross-country championships from 1950 to 1964.
He was a member of five Otago teams that won the New Zealand cross-country teams race in the 1950s and his best individual performance was to finish runner-up to Kerry Williams (Otago) at Timaru in 1955.
Cain has done his bit as an administrator at the national level and was a New Zealand cross-country selector from 1977 until 1992 and chairman for 11 years.
He was manager of the New Zealand team that competed at the world cross-country in Madrid in 1981 and was elected president of Athletics New Zealand in 1992-93.
Bates is on holiday in Europe with her husband, Craig, and will not return to Dunedin until the middle of next month.