Former Republic of Ireland international makes the move to the MLS by joining the Caps after his release from Leeds United
The 33-year-old centre back had only been a target for Whitecaps boss Martin Rennie for over a week when it emerged that he had been released from his contract at Championship side Leeds United.
Speaking to the club's official website, O'Brien said that he was looking forward to the challenge that is presented by the MLS.
“Not many people get the opportunity,” O’Brien said “But the opportunity arose, and what a club to be joining.”
“I’ve seen the stadium, I’ve seen the training facilities,” O’Brien continued. “It’s pretty impressive, isn’t it?”
“Ultimately, it’s my decision,” he added. “I have to suffer the consequences, good or bad, of my decision. I’m a big boy now. It was important to come and view the place, and get a feel for the place.
"Having done that, I’m very much looking forward to the future,” concluded O'Brien
Whitecaps manager Martin Rennie said that the club is 'really pleased' about securing the veteran defender's signature, noting that O'Brien was 'hungry'.
“He’ll add a lot of competition to our team. Competition that we’ve not really had at centre back for a little while now," said Rennie.
He added: "We’re really pleased overall about it, and for me, getting a player who’s really motivated and hungry and determined to make a big impact on his career in Major League Soccer was too good of an opportunity to turn down."