The former Liverpool left-back returned to English football after a three-year absence on Wednesday, joining Fulham for an undisclosed fee from Serie A side Roma.
Riise's move will see him link up with brother Bjorn Helge in west London, as well as fellow Norway international Brede Hangeland.
The 30-year-old came up against the pair in Fulham's 2010 Europa League run while at Roma and admits it will be special to now play alongside them.
"It was the first time my brother and I played against each other at a high level so it was a big experience for both of us," he told the club's official website.
"I managed to score against Fulham - my brother likes that one - and we enjoyed it, but now we can finally play together in a club.
"[As for Brede], we play next to each other in the national team and hopefully we can do the same here at Fulham.
"It can only help both Fulham and the national team that we can play together so having three Norwegians at the same club is going to be nice and we're going to enjoy it."
While the left-back admits he will enjoy playing alongside his brother and international team-mate, he insists they did not need to persuade him to join Martin Jol's side.
"Even before I knew of the interest I had heard a lot about how Fulham treated players - how they operate, all the physios, doctors and everything around the club," said Riise, who almost joined the club 10 years ago.
"I knew it was a great club to come to so I didn't need too much convincing because I knew already.
"But obviously now that everything is done I am really happy and looking forward to starting training and being fit for the season."
Riise is the club's second signing of the summer, following the deal for Hungarian goalkeeper Csaba Somogyi earlier this week.