The 22-year old has signed a three-year deal with the Bulldogs, tying him to the club until at least the end of 2023.
Allan joins Belmore with the opportunity to play at fullback, his preferred position, while he can also play as a wing.
Bulldogs chief Andrew Hill was thrilled with the addition of Allan.
“With what we believe has been an excellent off-season in terms of adding quality to our playing group, Corey’s signing is another great step forward in regard to what we are building here at Belmore,” Hill told bulldogs.com.au.
“By adding a State of Origin player to our squad and someone who has the potential to continue to grow as a footballer, we believe it is a major positive for our club and fantastic news for our Members and fans.”
Canterbury coach Trent Barrett added: “We have worked hard in the off-season to sign the right players in terms of their ability and attitude and we believe that Corey will be a great addition for our club.
“Everyone has seen what Corey can do over the past two seasons and we believe that he has the potential to be an outstanding player and someone that adds both quality and versatility to our backline.
“Corey will join us immediately and start training with the squad from today and everyone is looking forward to him being part of the Bulldogs.”
Allan has played 29 NRL games all for the Rabbitohs since making his debut in 2019.