The 28-year-old said: "I've been in a few days now and it's been brilliant. Obviously not all the boys are back yet but the stadium's fantastic and the weather's been superb! I'm a happy man.
"I'm really looking forward to the new season. The squad did well towards the end of 2008-09 and it shows that there's a lot to come. There's a great amount of exciting youth in the squad - like Jonathan Davies who's just won his first Wales caps - and I hope I can add something with my experience.
"There is a very promising new batch of young players coming to the fore especially in the backs, so if these younger boys can stick together for a couple of years then it'll be great to see them in action when they peak.
"I'm excited to be making a return to the Magners League after some time in the Guinness Premiership - and I'm looking forward greatly to the challenge of the Heineken Cup. To draw Leinster, the European champions, is a real test for us but hopefully we'll be able to spoil a few parties."
Perth-born Lamont said: "I'm thrilled to be here. Nigel Davies and his coaching staff are building an exciting squad and are based at one of Europe's finest rugby facilities. I think pre-season training will be pretty tough but I feel in good shape; I'm over the injuries I've had in recent years and I'm eager to start working up more speed and power.
"I'm determined to make a major contribution on and off the field. The Scarlets supporters can expect a massive amount of commitment and dedication from me."
Scarlets head coach Nigel Davies said: "It's good to have Sean at the region; he's already made an impact and adds to our developing mix of youth and experience.
"On the field he'll bring pace, great power and considerable skill to our backs unit. He's a seasoned professional - a top-class international with a proven record and has been playing really well for the Saints recently. He fits well into our set-up, will have an impact on the field and help raise the game of some of our younger players."
In 2007 Lamont won the Scotland player of the season award. In 20 club appearances last season, he touched down six times. One of those tries came in November's EDF Energy Cup victory over the Scarlets at Franklin's Gardens.
His international career has brought seven tries, his latest cap coming against Wales in this season's Six Nations in February 2009 at Murrayfield. He played in four of Scotland's five 2007 Rugby World Cup matches and has also represented Leicestershire Colts, Scottish Exiles and Scotland A.
Sean Lamont fact file
DOB - 15th Jan 1981
Birthplace - Perth, Scotland
Height - 1.88 m (6ft 2in)
Weight - 100 kg (15st 10lb)
Position - Wing
Honours - Scotland (37 caps)