The former The Hills hunk proposed to model Ashley Slack in November (12), according to Us Weekly, and the couple is planning to wed in October (13).
Slack went public with the news on Facebook.com by posting a photo of her engagement ring and the message, "I said yes! I am the happiest girl in the whole wide world and I cannot wait to spend the rest of my life with my best friend."
Wahler also shared a photo of his fiancee's ring on Instagram, adding, "Love you babe."
The reality Tv bad boy has previously revealed that his relationship with Slack is the first he's "ever been in sober", adding, "It's a little bit different when you're not drinking and going out."
Wahler cleaned up his act on Vh1's Celebrity Rehab in 2010 after six alcohol-related arrests.
It's the second piece of wedding news from former stars of The Hills so far this year (13) - another Conrad ex, Doug Reinhardt, became engaged to his high school sweetheart Allie Lutz over the holiday season and announced the news on Sunday (06Jan13).