The model sat at the head of the dinner table with the bride and her new brother-in-law, James Cook, and looked happier than ever at the family event.
The 21-year-old donned a white lace dress with a blazer on top and accessorized her ensemble with a white rose floral crown.
And throughout the romantic celebration, Cara snapped pictures of the happy couple with a disposable camera.
Just a week ago, Mr. and Mrs. Cook tied the knot at a beautiful ceremony at St. Paul's Church in London in front of close friends and family.
Cara, like the bride, wore a Chanel Couture gown, and was reportedly one of 17 bridesmaids.
The wedding party also included a number of page boys, including one dressed as a teddy bear!
Poppy's wedding comes just three months after Cara served as a bridesmaid at sister Chloe Delevingne's nuptials. So many weddings!
There were also several famous faces in attendance including Spice Girl Geri Halliwell and composer Andrew Lloyd Webber.
Cara documented much of the event on her Instagram and posted a picture of Poppy smiling in the back seat of a vehicle as she's being driven to the church, with the caption "Gorgeous Bride."
Cara posted another photo showing the invitation and wrote, "The big day."
Congrats to the happy couple!