The chief football writer of the Herald Sun, who has the media centre named after him at AFL House, told his colleagues on Monday he would putting away his pen after more than 40 years in the industry.
Sheahan began his career in newspapers on the Werribee Banner, beginning his football journalism career covering the VFL for Newsday in 1969.
After stints at The Age and media director for the AFL, Sheahan has been the Herald Sun's chief football writer for 18 years.
Sheahan won countless awards over his career, and as AFL coverage grew so did his influence, becoming a key contributor to Fox Sports and on radio.
Over the 2011 season, Sheahan was the first to write definitively that Mick Malthouse would be leaving Collingwood at the end of the season - a prediction which came true after the Magpies' grand final loss.
Colleagues and football fans took to social media to pay tribute to Sheahan's career.
"Mike Sheahan the guru, great friend to me and many, is retiring. #Standingovation," tweeted Herald Sun colleague Mark Robinson.