Smith has joined the Championship outfit for an undisclosed fee as he seeks regular first-team football.
The 22-year-old – who has made just two appearances for Tottenham – has spent seven stints out on loan, including a season-long switch to Bournemouth in the 2010-11 season.
"It's great to be back," Smith told Bournemouth's official website.
"My loan spell here a few years ago was successful and I've worked with (manager) Eddie Howe before, so it just feels right.
"This is what I need because hopefully I will get some games to improve myself and help the club move up the table.
"I've had seven loans and I was looking to stay at one club for a while. At this stage in my career, I need to have a home."
Bournemouth manager Eddie Howe was delighted with the signing, adding: "We are really pleased to bring him in permanently.
"Our wish is always to sign young talent, develop it and make it better and I think Adam certainly fits that profile.
"A year ago, he was England Under-21's regular right-back so that shows what a good player he is."
Smith is not expected to feature in Bournemouth's home fixture against Huddersfield Town on Tuesday.
