Henson had been linked with a host of other sides in England, France and Wales but has put pen to paper with the Blues despite them being bitter rivals with former outfit the Ospreys.
The 2005 Lion made it clear that he wanted to play fly-half last year but he was employed in his more customary position of centre by Wales in the summer and is likely to swap between the two for the Blues.
"I've been saying I wanted to play back in Wales and I'm glad of the opportunity that Cardiff Blues have given me," said Henson, whose self-imposed 19-month exile from the sport came to an end when he initially signed for Saracens late in 2010.
"I just want to do everything I can to make them happy and enjoy my rugby. I'm glad I've signed here.
"The Blues have always had a great squad and there's no change there with all the youngsters that they have. They are strong at centre and strong at outside half, so it's up to the coaches where they want me to play.
"There's been huge rivalry between the Blues and the Ospreys over the years, and I've been part of that, so to leave and join the Blues is a bit strange. I'm sure when I meet up with all the boys it will be fine as I know most of them. When I do run out for my first game for the Blues, I will be Blues through and through.
"The facilities I've seen at the Blues, from the training facility to the stadium, are incredible. It's a very exciting time for me."
Henson is currently recovering from the wrist injury that ended his World Cup dream during the August warm-up fixtures and, although no official date has been set for his return to full fitness, he is desperate to make his Blues debut as soon as poosible.
"The wrist is coming along alright. Obviously it was a nightmare injury for me, but I'm two weeks out of plaster now, so maybe a couple of weeks before I'm back on the pitch," added Henson, who could feature in the Heineken Cup group games in November having beaten Thursday's deadline for European registrations.
"It was nightmare timing getting that injury just before the World Cup, but these things happen. It's pretty tough mentally now, but it's healed and getting stronger, so I'm just looking forward to playing for the Blues.
"Going into the England game for Wales, I was feeling great physically. I'd done a lot of work with Wales and a lot of training, so I've tried to maintain that as best as I can, but some things are difficult because I was in plaster.
"I hope over the next few weeks now that the plaster is off that I will do other conditioning. I'm dying for the first opportunity with the Blues."