Smith, 26, told Brisbane last week he was seeking a fresh start, but called time on his career via social media on Monday night.
"I’ve been sitting on this for a long time now, but perspective, priorities and the importance of wellbeing have led me to the right choice," Smith said.
"I walked into the Brisbane Lions an 18-year-old who’d never kicked a footy and was expected to last a year as a project player.
"Eight years of pro football later I’m retiring, super proud of the memories I’ve made and the relationships I’ve gained."
He made his debut in 2016 against Port Adelaide, gathering 19 disposals, including nine clearances, and affecting 30 hit-outs, going on to play 16 matches in his career.
Smith has had a tumultuous 12 months following the death of his brother Sebastian by suicide, initially taking time away from the Lions to take care of his own mental health.
"There’s a whole big world outside the footy bubble and I’m excited to see what that holds for my family and I," he said.
"I’ll always be a proud Lion."