El Moussa proposed while celebrating his and Young's one-year anniversary over the weekend.
UPDATE: Tarek El Moussa and Heather Rae Young shared a new pic of his proposal on Thursday.
"This is the exact moment I got down on one knee and asked @heatherraeyoung to be my wife!" El Moussa captioned the pic on Instagram. "You just never know where life is going to take you. If you told me 13 months ago I would be engaged today I would have called you crazy. You just can’t predict what’s going to happen."
"One moment you are sitting there and the next your life is completely different. The second I saw @heatherraeyoung I knew my life would never be the same. She’s not only become my best friend but she’s also incredible to Tay and Bray. Some of you have followed me for years and have supported me throughout my struggles. I want to say thank you and I couldn’t have gotten here without you!" he added. "Now...who wants to see the RING??:)"
Young shared the same pic, writing, "The future Mrs. Heather Rae El Moussa!!! ?❤️ This was the best day of my life!! This moment when @therealtarekelmoussagot down on one knee & asked me to spend the rest of my life with him. SO much to tell you guys, I’ll give you the inside scoop throughout the next few days on how I was feeling throughout the weekend. He kept everything a secret from me. I knew he had little surprises throughout the weekend, but I thought he was just being extra romantic for our one year. Little did I know he had been planning to propose."
"I couldn’t see anything as I was walked down to the beach. There were cabanas lined up covering everything. I was rushed around the corner to what I thought would be a dinner on the sand. But when I walked around the corner Tarek was standing there looking so handsome in his tux. I was confused for the first 15 seconds as I walked down the gorgeous candle & flower aisle wondering what the heck is going on. Then I thought OMG is he proposing??? No way!!!! But in my head I talked Myself out of it thinking well I bet it’s earrings!!! I didn’t want to get my hopes up," she continued. "More to come tomorrow!!!!! I can’t wait to marry you @therealtarekelmoussa❤️."
The pair announced the news on Instagram early Sunday morning, each sharing a photo of El Moussa's proposal at Descanso Beach Club on Catalina Island. The Flip or Flop star is dressed in a tux as he slides a ring onto Young's finger in the pic. The Selling Sunset star, wearing black dress, smiles from ear to ear.
"She said yes! #FlippingHerLastName @dukeimages," El Moussa captioned the pic on Instagram.
Young wrote on her page, "The Future Mrs. Tarek El Moussa!!!! @dukeimages."
Well wishes quickly poured in for the couple. Young's Selling Sunset co-star, Amanza Smith, commented, "OMG!!!! I was soooo hoping this would happen during your amazing anniversary adventure! Congratulations babe! ❤️❤️❤️❤️❤️???????? big hugs to you both!! Xoxoxo."
El Moussa, 38, confirmed his relationship with Young, 32, last August. The two moved in together in January. In a May interview with ET, Young said she would love to take the next step in her relationship with El Moussa -- but wasn't in any rush.
"We just have the best time together. He's my best friend in the whole world and I'm just really enjoying what we have right now. I don't feel like there's a rush," she shared. "And honestly, I want him to feel a hundred percent ready. He went through a very public divorce. He went through a really rough time, and I want him to do it when he feels ready. And like I said, I’m loving life and I'm loving every single day with him and the kids and I'm not in a rush. I mean, do I wanna be engaged? Of course, who doesn’t. But I'm not pushing him."
This will be the second marriage for El Moussa, who separated from ex-wife Christina in 2016. The pair share two children: daughter Taylor and son Brayden. She has since remarried, to TV personality Ant Anstead.
Young told ET in May that she and El Moussa committed to each other after just two dates. She said she was happy to be a "bonus mom" to his kids, and has a great relationship with his ex.
"I've never been a mom. I'm new to all this," Young explained. "But as a woman, I just kind of felt like, 'What would I want being in her situation?' So it felt only right for me -- that I'm gonna be living with the children, being around the children all the time -- that I would reach out to her. And we have a great relationship. We talk about the children and it's great. It's been such an amazing experience for me being this new 'bonus mom.'"
See more on El Moussa and Young in the video below.
(This story was originally published on July 26 at 9:26 a.m. PT)
Heather Rae Young on Her Relationship With Tarek El Moussa's Ex Christina and When He'll Propose (Exclusive)
Tarek El Moussa Shares Sweet Pic of Girlfriend Heather Rae Young 'Chillin' With Son at Daughter's Soccer Game