Lifestyle Style Kristin Cavallari Sports Chic Black Ensemble as She Celebrates Her 35th Birthday "35," Kristin Cavallari simply captioned a photo of herself on her special day By Olivia Jakiel Olivia Jakiel Instagram Associate Editor, Nights – PEOPLE People Editorial Guidelines Published on January 5, 2022 09:19 PM Share Tweet Pin Email Photo: Kristin Cavallari/instagram Kristin Cavallari is totally dunzo being 34. The Very Cavallari star celebrated her 35th birthday on Wednesday, showcasing her stylish outfit on Instagram in honor of her big day as she posed next to a simple yet chic display of gold balloons that spelled out "Happy Birthday." The Laguna Beach alum looked sleek and ready for a night on the town in an all-black getup, which consisted of curve-hugging bottoms, a low-cut top with a sweetheart neckline, a structured blazer, and strappy sandals. Kristin Cavallari Calls Split from Jay Cutler 'Probably the Best Decision I've Ever Made' The Uncommon James founder's friends flocked to the comment section to send their best birthday wishes on her special day, including Cavallari's former The Hills costar Heidi Montag, who wrote, "👏👏👏👏👏👏 Happy Birthday hot mama!!!!!!!❤️💋🥰." Model Lily Aldridge added a chain of heart emojis. Never miss a story — sign up for PEOPLE's free daily newsletter to stay up-to-date on the best of what PEOPLE has to offer, from juicy celebrity news to compelling human interest stories. BFF and Very Cavallari costar Justin Anderson was also there to celebrate the momentous occasion, as he posted a video of the reality star's balloon decorations on his Instagram Story – including one of the balloons that fell down, making the display hilariously spell out "Happy Birth ay" Additionally, Anderson posted a picture of what appears to be Cavallari's birthday cake on his Story, captioning the sweet snap, "happy happy to my best fren." Heidi Montag Shares Honest Message About Trying for Baby No. 2: 'Never Thought It Would Be So Hard' Justin Anderson/instagram Cavallari's birthday celebration comes just one week after she and her family, including sons Camden Jack, 9, and Jaxon Wyatt, 7, plus daughter Saylor James, 6, headed to the mountains for a fun-filled ski day on the slopes. Cavallari shares all three children with ex-husband Jay Cutler. RELATED VIDEO: Kristin Cavallari on Her Worries of Raising Kids in Spotlight: 'I Only Care if They're Happy' In December, a source told PEOPLE that the Balancing in Heels author and Cutler were focusing on co-parenting their children ahead of the holidays. "Kristin is looking forward to spending the holidays with the kids. They'll be having a quiet Christmas at home in Tennessee," the insider said. Added the source: "They've worked really hard to get to a good place and manage the kids and the holidays and are doing their best to keep it positive and friendly. Things have gotten better recently."