"It's always a wrench to leave your first club. I have been at Huddersfield since I was ten," Stead told the clubs official website.
"But I am a Blackburn player now, though I'll always have an eye out for their result.
"It wasn't a tough decision. Once I had been to Ewood Park and to the training ground it was quite straightforward.
"I just can't believe what's happening to me. I'm a little bit lost for words, but I can't wait to get involved as it's a fantastic opportunity."