The proud mom celebrated her daughter's special day with a look back at moments from her childhood.
Moore took her fans on a walk down memory lane with a slideshow of throwback photos taken through the years, beginning with a black-and-white snapshot showing the proud mom holding her little girl in her arms when she was a baby.
"Words can not do justice to the love, gratitude and joy I have for you," Moore captioned the post. "You are a magnificent woman but you will always be my baby..."
Moore added, "You changed my life and gave it meaning beyond anything I had ever known. Happy Birthday, Rumer Glenn! I love you forever and a day❤️"
The slideshow also included a photo of Rumer in a houndstooth jacket, sweater vest and an elf-cap, as well as a photo of a young Rumer hugging her mom while Moore wore nothing but lingerie on the set of her 1996 film Striptease.
Rumer's sisters Tallulah and Scout -- whom Moore shares with ex-husband Bruce Willis -- also honored their sister's birthday with fun Instagram posts.
"Rumer is my best friend. I have the privilege of sitting next to her outside right now so let me just narrate what I am seeing: She is in the deep splendor of her 32 year, radiating the ultimate glow that comes from being a genuinely good person and being committed to always growing and learning about herself in service to emanating ever more compassion, love and grace," Scout wrote, alongside a slideshow of different throwback pics.
"Her being my big sister means that I’ve never had a minute of my life without her, and I wouldn’t want it any other way," Scout added. "I just LOVE you so much @rumerwillis, so now i am gonna log off and tell you all of that in person."
Meanwhile, Tallulah shared a photo of the three sisters standing together in matching yellow gowns near a lake, and wrote in the caption, "We love our Rue."
Rumer also reflected on her birthday, which she said was "one of the most special celebrations of my birth I have ever had."
"I am so excited for this year, my own personal New Years. This year I set the intention to let go of anything and everything that no longer serves me and trust that the universe is setting me up to have the life I have always dreamed of," Rumer wrote on Instagram, alongside a handful of photos showing how she commemorated her special day.
"For those of you who I don’t get to share my day with, I am endlessly grateful for your love and support," she added. "The way you all love me helps me love myself. I am so grateful for you."