The 30-year-old reluctantly delivered the news to his teammates more than a year after he experienced a delayed concussion against Carlton.
Adams was placed on the inactive list in January and allowed time to recover before further medical advice to cease participation in contact sport prompted Wednesday's confirmation.
"No prizes for guessing why I'm standing here," Adams told his teammates in vision supplied by the club.
"It's time for me to give it away, officially.
"I've been waiting for the time to come where I might feel good enough to be able to start training or do something again to get back to playing.
"It hasn't happened for me yet, don't know if it will."
Constant injuries meant the former Western Bulldogs back was restricted to 73 games across seven seasons.
But late in his fourth year at Brisbane he had established himself as a vital cog in a Lions side that had risen from easy-beats to top-four regulars since his arrival.
"What Fages was selling was a vision he sort of delivered on," Adams said.
"It's been such a pleasure to be part of and a pleasure to watch this year from afar. It's hard knowing I won't be a part of it anymore."
An emotional Fagan had to compose himself after choking up during his tribute to the retiring Adams.
"I'm so sad that it's come to this," he said.
"It took me about 30 seconds to work out you were a good person (when recruiting him).
"Then I started to learn what a professional you were.
"What you will be able to say was that you got the best out of yourself ... and that's all you can hope for."
Brisbane finished the regular season in second and will host Port Adelaide at the Gabba next Saturday.
"When we run out for the finals, mate, we run out with you in our heads and will give it our best shot," Fagan said.
"Thanks for all you've done."
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