The oldest daughter of the "Crocodile Hunter" and Terri Irwin posted a throwback family shot and began her message directing it straight to her dad.
The photo shows the four family members and a little Bindi holding a thumps up while posing next to her dad.
Steve is holding their son and Bindi's younger brother, Robert, in his arms.
"Dad, You would be so incredibly proud of Robert," she began her message. "He has been such an amazing support during this beautiful new life chapter."
Bindi also included a picture with Robert and her soon-to-be husband, Chandler Powell, and revealed her brother will be stepping into Steve's place and walking her down the aisle.
"I know you’d be beaming with pride when the time comes that he walks me down the aisle," she shared.
Bindi ended her message on a heartbreaking note.
"I wish you could be here for these moments," she wrote, "but I know that your spirit lives on in us."
Steve Irwin passed away in 2006 after being stabbed by a stingray when Bindi was just 8 years old.
Bindi announced she got engaged to Powell on her 21st birthday in July.
"On my birthday I said ‘yes’ and ‘forever’ to the love of my life," she wrote at the time.
"Chandler, close to 6 years ago I fell in love with you and every day since has been a whirlwind of adventure and true happiness."
Days ago, she wrote how thankful she was for her family and shared a photo with her fiancé, her mom and her brother.
"Thankful to have such a beautiful family to hold my hand and share life’s most magical moments," she wrote.