The 34-year-old singer congratulated Kerr, the ex-wife of her fiancé, Orlando Bloom, on the launch of her Kora Organics skincare line after attending the event Thursday in Malibu, Calif.
"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.
"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."