The New Zealand born player is 6'2" and weighs over 16 stones and now has EQP status through residency.
London Irish Director of Rugby, Brian Smith, is delighted that Blair has penned a three year deal with London Irish saying: "Blair Cowan is in great form at present and he's a player we've been tracking for some time. Blair is a great fit for us, he can play all three back row positions and he's a try scorer. There are a lot of tough players in this league but not a lot tougher than this guy."
Blair Cowan said: "I'm looking forward to moving down South and joining London Irish. There are a lot of great players at the club and a lot of potential to match. I would like to thank Worcester Warriors and wish them all the best for the future."