The 30-year-old proposed Biel, 27, last month during a pre-Christmas break in Jackson, US, after they reunited following a three-month split.
“Justin knows how much she loves snowboarding and the mountains, so it was the perfect place. This was the basis for getting back together. When they reunited, they had a conversation about taking the next step,” femalefirst.co.uk quoted a source as saying.
The couple, who have dated on-and-off for the past four years, celebrated their engagement with their family and friends at Timberlake’s home in Big Sky, Montana.