Ann Pearl Hudson was the pop singer's paternal grandmother. The black-and-white clip was part of a series of photos and videos the 35-year-old "Roar" singer posted in tribute to her grandma on Monday.
"Grandma, it's Katy. Grandma, it's Katy," Perry says in the video. "I just wanted to tell you I know you're not feeling well, but I wanted to share some exciting news with you. You remember me, Katy? I'm gonna tell you that I'm gonna have a baby. I'm pregnant, Grandma."
"Don't tell anybody," someone offscreen jokes.
"Uh-uh," her grandmother replies.
"Don't say 'uh-uh!'" Perry says with a laugh.
Perry is expecting her first child with fiancé Orlando Bloom. She announced the big news last week in a music video for her single, "Never Worn White."
Her Instagram tribute also featured several other photos and videos of her and Hudson together, including moments with President Obama and Bloom.
"Ann Pearl Hudson was a fighter," she wrote in the caption. "She survived the Great Depression, raised 3 kids on her own as a seamstress, making G strings for showgirls and other such characters in Vegas. She was always authentically herself, funny and full of all the sweet cozy things you think of when you think of grandmas.
"She gave me crisp dollar bills in hallmark cards, she let us eat her favorite almond cookies from the 99 cent store while we asked questions about the different fans she had on display on her walls. She was a wonderful grandma and I will forever carry some of her in me."
The "American Idol" judge also shared how she believed Hudson's spirit would live on.
"When my whit comes out, that's Ann. When my authenticity comes out, that's Ann. When my stubbornness comes out, hell, that's Ann. When my fighter spirit comes out, that's Ann. When my style comes out, that's Ann," she wrote.
"May she rest in deep peace and kiss the forehead of the soul to come and let them know everything is gonna be OK, especially now that they have gained an angel to look over them."
Perry made her first public appearance since her pregnancy announcement at the ICC Women's World Cup 2020 Final in Melbourne, Australia, on Sunday.
She later performed a concert where she told the crowd she was rooting for a daughter.
"I hope it's a girl," she said during the opening of her song "Wide Awake," according to a video that was shared on Twitter.