The couple decided to walk down the aisle after dating for six months.
Kroeger reportedly presented Lavigne with a 14-carat diamond ring August 8 and a representative for the punk-rocker has confirmed the news, the Hollywood Reporter said.
The announcement comes as a surprise to Lavigne's fans as she had been dating Brody Jenner since mid-2010 before reportedly splitting in January of this year.
Prior to that, Lavigne was married to Sum 41 frontman Deryck Whibley for three years. They divorced in 2009.
Lavigne, 27, and Kroeger, 37, first got together in February to co-write a song for Lavigne's upcoming fifth studio album.
