The 44-year-old actress spent time with Diaz, Richie and Burch at her "In Goop Health" conference Saturday in Culver City, Calif.
"Dream girl band @camerondiaz @nicolerichie @toryburch #ingoophealth," she captioned a photo on Instagram of herself with the trio.
Paltrow, Diaz, Richie and Burch spoke about health and fitness during the event. Paltrow said in her opening remarks that her interest in well-being began after her dad, Bruce Paltrow, was diagnosed with throat cancer.
"I went from a chain-smoking Camel Lights kind of girl to trying to understand why my dad had cancer," the star recalled, according to Vogue.
"I still feel like my role is to ask questions and open people up to things they never would have heard of before," she added. "I'm not saying it's for everyone, but this is really validating, meeting all the readers and bringing them together with the experts."
Diaz, meanwhile, explained her retreat from Hollywood during the "Balls in the Air" panel, according to E! News. The 44-year-old actress last appeared in a 2014 remake of Annie.
"I just went, 'I can't really say who I am to myself,' which is a a hard thing to face up to," she said. "I felt the need to make myself whole."
Paltrow launched Goop, a lifestyle website, in 2008.