The "Watch What Happens Live!" host posted a photo of the famous socialite and heiress, who passed away on Monday at the age of 95.
"Gloria Vanderbilt was an amazing woman who lived a life filled with incredible peaks and impossible obstacles," he wrote. "Through it all she remained eternally optimistic with a wicked sense of humor. In fact, Anderson's iconic and infectious giggle comes from his mom."
Andy added, "Sending Anderson all my love, and may she Rest In Peace."
The CNN host announced that his mother had passed away after a bout with cancer.
"Earlier this month, we had to take her to the hospital. That's where we learned she had very advanced cancer in her stomach and that it had spread," he said in a video. "When the doctor told her she had cancer, she was silent for a while, and then she said, 'Well, it's like that old song: Show me the way to get out of this world, because that's where everything is.'"
"Love is what she believed in more than anything," he continued. "Gloria Vanderbilt died as she lived: on her own terms."
In a statement to CNN, Anderson said, Gloria "was a painter, a writer and designer but also a remarkable mother, wife, and friend… She was 95 years old, but ask anyone close to her, and they'd tell you: She was the youngest person they knew — the coolest and most modern."