The 30-year-old becomes the third new face to arrive at Rovers in the January window, joining on loan from the Premier League side until the end of the season.
“It’s been a mad 24 hours, I was training with Sunderland yesterday morning and then I came down here last night to get things sorted, so I’m delighted to get it done, I’m looking forward to the first game against Charlton and hopefully we can get off to a flying start,” said Graham.
“I was aware of the interest in the background and obviously I’ve been playing a bit at Sunderland the last few weeks, so I’m coming here with games under my belt, which is also pleasing, so hopefully we can both do well for each other.
“I spoke to the manager a few times and obviously he’s got some good players. The transfer embargo has been lifted, so they want to sign players and move the club forward. For me to get out of Sunderland and have a fresh challenge is superb for me, so I’m delighted to get it done, I can’t wait to get going and hopefully we can pull together and move up the table.”
Gateshead-born, Graham started his career at Middlesbrough, making his debut as a 19-year-old against Manchester United at Old Trafford in October 2004.
His four years at the Riverside saw him go out on loan to a number of clubs across the divisions including Darlington, Derby County, Leeds United, Blackpool and Carlisle United, before he made a permanent move to Brunton Park in 2007.
Following a successful spell with the Cumbrians, in which he scored 40 goals in 113 appearances, Watford came calling in 2009.
Graham was a big hit for the Hornets, twice finishing as the club's top scorer, as well as equalling Watford’s record for the most goals scored in consecutive games when he found the back of the net in seven successive fixtures.
After an impressive two seasons at Vicarage Road, Swansea City secured his services for £3.5m in 2011. During his time in South Wales, the striker scored 21 goals in 62 games.
Sunderland then spent a reported £5m for Graham in January 2013 and whilst at the Stadium of Light, he had loan spells with Hull City, Middlesbrough and Wolves.
Graham is expected to go straight into the Rovers squad for this weekend’s Championship clash with Charlton, but he is ineligible to play in next weekend’s Emirates FA Cup fourth round tie at Oxford having already played in the competition for Sunderland.