The 36-year-old star - who welcomed daughter Daisy Dove with her fiance Orlando Bloom in August last year (20) - teamed up with her partner's ex-wife at Malibu's Jonathan Club, where they had a wellness day with trainer Nichelle Hines and model Josephine Skriver.
Alongside some videos, she wrote, "Spent me #wellnesswednesday with my gal @mirandakerr. First time I did yoga since being preggers... let's just say I enjoyed Shavasana okkkk. (sic)"
Miranda shared the post with her own followers, adding, "I love you Katy Perry."
The "Roar" hitmaker has previously opened up about her "close" relationship with Orlando's ex-wife, with whom he shares 10-year-old son Flynn.
"In our modern family, she's probably the most health-conscious of everyone," Katy said. "One of the great things about being close to Miranda is I get to try out all her products, especially when her son (Flynn) comes home with them in his backpack."
Meanwhile, Miranda thinks Orlando's romance has made him happier than ever which, in turn, has made him a better father to their son.
"I just feel so happy that Orlando found someone that makes him happy, because at the end of the day, for Flynn to have a happy father and a happy mother is the most important thing," she recently said.
The Kora Organics founder is now married to Evan Spiegel, with whom she has three-year-old Hart and Myles, 21 months.