The couple announced their engagement on Monday but reportedly will take their time in planning an official ceremony.
"They haven't set a date. They're really enjoying this moment," a source explained to People."They have the same values and really understand each other. They complement each other and are so happy."
Lavigne and Kroeger themselves opened up about their romance - which blossomed while working together on Lavigne's new studio album in February 2012 - in an interview with Hello.
"I knew I was falling for her. It was incredibly powerful and something I'll never forget," Kroeger recalled of his time with the 'Girlfriend' singer in the studio.
Asked what attracted her to Kroeger, Lavigne answered: "He makes me laugh every day. He takes care of me in every way and is extremely attentive."
Lavigne was previously married to Sum 41 singer Deryck Whibley for three years. The pair divorced in 2009.
Watch Avril Lavigne's video for 'Sk8r Boi' below: