The 36-year-old has made 25 first-team appearances for the Cherries since signing on a free transfer from Reading in June.
"I think Ian's experience has been key for us," manager Eddie Howe told Bournemouth's official club website. "He knows how to manage games.
"He's been at the very highest level in world football. He's seen it, been there and done it and that can only help the players around him."
Harte, whose previous clubs include Leeds United, Levante and Sunderland, is the Republic of Ireland's joint-11th all-time record goalscorer, having netted 11 times in 64 senior internationals.