The 28 year old said that he was looking forward to working under Michael Bradley at Connacht.
"I'm excited to be joining a Connacht side which is very competitive and gaining great impetus under the guidance of Michael Bradley and Eric Elwood.
"Obviously with Michael Bradley at the helm, I'm sure he'll have a significant influence on how I play, having been a former Irish scrum half himself."
Campbell, who was with London Irish from 1997 to 2001 before signing with Ulster, was part of the U19 World Cup winning side in 1998 and is looking forward to playing once again with players he would have met in various international squads.
"Connacht is a squad with great potential and I'm looking forward to getting the opportunity to playing again with former team mates, having grown up with Adrian Flavin at London Irish and of course Johnny O'Connor and Gavin Duffy for Ireland."
Connacht CEO, Gerry Kelly, is delighted to sign such an experienced player and is impressed with Campbell's ambition.
"Kieran sees this as an opportunity to push himself back into the Irish setup. While playing at Ulster he has been frustrated by the lack of playing opportunities due to the success of Isaac Boss and with that in mind he is a great asset for us to acquire for the forthcoming season," said Kelly.
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