The 35-year-old was recently named assistant manager at London Road following a brief spell at Linfield.
McCann's former clubs include West Ham United, Notts County and Barnsley.
"I have had so many highs during my playing career and I look back with great pride," he is quoted as saying by Sky Sports News.
"Now I want to concentrate on helping the young lads at Peterborough flourish and pass on my knowledge to them. I can concentrate on being the best coach I can possibly be for the football club that I love."
McCann scored four goals in 39 appearances for Northern Ireland during an international career that lasted from 2001 to 2012.