The 34-year-old singer and "American Idol" judge congratulated Kerr, the ex-wife of her fiance, Orlando Bloom, on the launch of her Kora Organics skincare line after attending the event Thursday in Malibu, Calif.
Perry shared a photo on Instagram with Kerr, who is pregnant with her third child.
Kerr married Snapchat founder Evan Spiegel in May 2017.
"KORA-grats on an illuminating vitamin c packed to perfection product - The #Nonibright serum @mirandakerr @koraorganics (also, love u sissy)," Perry captioned the post.
Kerr had posted the same picture on her own account.
"Thanks for shining bright with me @katyperry & Angela @koraorganics #NoniBright," she wrote.
Fans voiced their admiration for Perry and Kerr in the comments.
FOLLOW REALITY TV WORLD ON THE ALL-NEW GOOGLE NEWS!
Reality TV World is now available on the all-new Google News app and website. Click here to visit our Google News page, and then click FOLLOW to add us as a news source!
"adults acting like adults THATS WHAT THIS IS and that's why they're GLOWING," one person wrote.
"I love a mature relationship," another added.
Kerr split from Bloom in 2013 after three years of marriage, and is parent to 8-year-old son Flynn Christopher with the actor.
She told Marie Claire U.K. in March she has a good relationship with Perry.
"We all get along really well," the model said. "We're like a modern family."
Perry and Bloom got engaged on Valentine's Day in February.
Perry discussed her early romance with Bloom on "Jimmy Kimmel Live!" later in the month, saying they bonded over In-N-Out.
Copyright 2019 United Press International, Inc. (UPI). Any reproduction, republication, redistribution and/or modification of any UPI content is expressly prohibited without UPI's prior written consent.