Brighton boss Steve Coppell moved for the Reading man after injuries and suspension have forced out Gary Hart, Paul Kitson and Bobby Zamora. In addition, the Seagulls last month missed out in the race to sign Steven Sidwell, who opted for a move to Reading instead.
Following the recent loan signing of Luke Chadwick, Rougier, who is out of contract in the summer, has found first team opportunities hard to come by, prompting him to make the switch to the South Coast.
Seagulls boss Steve Coppell was delighted to complete the deal which should aid his sides bid to stay in the First Division. Brighton have been performing well lately, defeating Wolves and Bradford in their last two outings.
Speaking to seagulls.co.uk, Coppell commented: "Anthony is a player I've watched for a number of years and I've always had the feeling that he's a player who can influence a game.
"He's a little bit of 'something else' - with suspensions for Zamora and Hart and injury to Kitson there aren't many options so I'm pleased with what Tony will bring us.
"It's been difficult finding someone, and I've been down a lot of blind alleys. Everything clicked with Anthony though, especially because of my relationship with Alan Pardew, so I'm very grateful for that."
Rougier, who has netted twice for Reading this season, could be in line to make his Brighton debut on Saturday when the Seagulls play host to Millwall. It is not yet known if there is any chance of a permanent deal.