Smith was due to come out of contract at the end of next year, when he would have been a free agent.
But a Swans spokesman confirmed on Monday that Smith had recently re-signed for one more season.
The Scotch College old boy is set to play his 100th AFL game in the Swans' round two clash with Collingwood at ANZ Stadium on Saturday week.
Smith has recorded three consecutive top-10 finishes in the Swans' best and fairest award, finishing sixth in 2011 and 2012 and ninth last year, and is often touted as a future leader of the club.
The defender was a key player in the Swans' 2012 premiership season, generally manning the opposition's best small forward.
In the Grand Final, he kept Hawthorn's Cyril Rioli and Paul Puopolo quiet for much of the game.
The 25-year-old is also a member of the Swans' leadership group, having joined the club as a rookie at the end of 2006.
