The 20-year old has enjoyed 29 appearances for the Dragons since 2011 and had international call ups from the Wales U20’s team.
“I would like to thank everyone at the Dragons for their support and I will be giving my all for the region for the rest of this season before I make my switch to the Blues,” he said.
Dragons Director of Rugby Lyn Jones said, “I am delighted for Ieuan; it’s a really good move for him. I wish him all the very best there.
“It’s important that he plays regular first team rugby and at the Blues he will get that.
“Maybe we will see him in a Dragons shirt again in the near future.”