Critchley left Blackpool 12 months ago to become Steven Gerrard's assistant at Aston Villa.
He then left Villa Park following Gerrard's sacking in October, before being appointed QPR head coach in December.
The 44-year-old was sacked by QPR just two months later after winning only once in 12 games.
"It feels special to be back and I'm thoroughly looking forward to the task that lies ahead," Critchley told the official Blackpool website.
"Looking back on my departure 12 months ago, I didn't handle that in the manner I should have done.
"I enjoyed a fantastic relationship with Simon (Sadler, Blackpool owner) previously, and I thank him for this wonderful opportunity to come back to this special football club.
"I look at the club now, and it has had a bump in the road but there is no reason why we can't get back on track.
"It's up to us - and I include myself in that - to reset and become who we were as a group again.
"Collectively, the staff, players and supporters have shared some special moments together, and I know we all want to experience that again, which is what we will be working towards."