Black told new coach Justin Leppitsch on Thursday evening that he was calling it a day after originally delaying the decision following post-season surgery on his groins and knees.
"I still absolutely love the game and have the passion to compete, but I just wasn't 100 per cent certain that my body could withstand the demands of another AFL season," Black said on Friday.
"My head and my heart were dragging me in two different directions, and I guess in the end the head prevailed.
"It was an incredibly tough decision, particularly as I've spent almost half my life playing AFL with the Brisbane Lions."
Brisbane hope the 34-year-old Black will move straight in an assistant coaching role with the club next season.
Black leaves the game as the most decorated player in the combined history of the Brisbane Lions, having played a record 322 games, won a Brownlow Medal and a Norm Smith Medal and played a key role in the 2001-03 premiership teams.
He is also a three-time All-Australian and triple Brisbane best and fairest winner.
Black finally decided to retire after scans following post-season surgery which revealed he risked permanent knee damage if he played on.
"That probably scared me," Black said.
"I changed my mind 100 times but I sat out under the stars the other night and thought my body had been so good to me over the years it was about time I did it a favour.
"I sit here now very comfortable with what I have achieved in my career.
"Playing another 15 to 20 games at best wasn't going to achieve a whole lot."
Leppitsch said Black could have "any role he wanted at the club".
"It's always a sad day when a club great leaves but he's also a great mate of mine," Leppitsch said.
"But I am happy for him. He's got a great family and hopefully a great career still ahead.
"Over the last couple of weeks my job was to mentor him through this process, there was no arm twisting.
"I would say he will win more awards in retirement than when he played which says a lot, he's a Hall of Famer."
Leppitsch hoped to know by next week whether Black would accept an assistant role with the Lions.
BRISBANE LIONS CHAMPION MIDFIELDER SIMON BLACK'S AFL CAREER STATS
Born: April 3, 1979 in Mount Isa, Qld
AFL games: 322
AFL goals: 171
Brownlow Medal 2002
Brownlow Medal runner-up 2007, 2008
Norm Smith Medal 2003
All-Australian 2001, 2002, 2004
AFL life member 2011
Lions premiership player 2001, 2002, 2003
Lions co-captain 2007-2008
Lions vice-captain 2009, 2010
Lions club champion 2001, 2002, 2006
Lions club champion runner-Up 2003, 2008, 2009, 2010, 2011
Lions Team of the Decade member 2006
Lions life member 2007
Lions Rookie of the Year 1999