'I wasn't like: "Oh my God, I am going to be in a bikini and Kate is going to be in a bikini and what is everyone going to think of me"'.
The beautiful blonde actress said she feels better about herself now than ever and wasn't worried about starring alongside the Sports Illustrated model in her new comedy film, The Other Woman.
'I am 20 years older than her. I am not trying to be her. She is a beautiful woman. We are completely different and I celebrate her,' she claimed.
Blonde beauties: Kate and Cameron enjoyed a cocktail in the sea together while filming their new comedy flick
Confident: The actress is a role model for body confidence, saying she feels better at 41 than ever before
Cocktail hour! The busty 21-year-old showed off her best assets in a red bikini after a long day of filming
'I don't wish I was 21 any more. I am very happy to be 41 and I love it. I feel great about my body. I take care of myself. It is important to me,' she added.
Cameron doesn't just appreciate Kate's looks, the pair have also been getting along great as friends after starring alongside Leslie Mann, 41, in the film which focuses on the plight of three women who seek revenge after discovering they have been cheated on by the same man.
Meanwhile, speaking to presenter Sophie Monk on the 2Day FM radio show on Thursday, Kate revealed how she really feels about her breasts, explaining she'd never said she wished they were smaller, despite previous reports of her doing so.
Sophie said: 'Kate, I want to be your friend because we share something in common. I've got really big boobs and I don't like them. I want to be like Cameron, where I see you running down the beach and having so much fun and mine are like smacking me in the face.'
'The grass is always greener, isn't it?,' Cameron laughed.
Outspoken: Leslie, Cameron and Kate set the record straight while speaking to Sophie Monk on 2Day FM
Setting the record straight about her enviable assets, Kate reasoned: 'I actually didn't say that. I love my body, and I didn't mean that. It's like you said, there are moments in every woman's life where you feel insecure. Life isn't perfect.'
She added: 'I really never said that... I just think that women can relate to not feeling their best, and I'm sure men can too, and just moments where you're feeling awkward and that you know, you don't want to run on the beach that day.'
Moving on, Sophie asked the three women who is most likely to drunk dial an ex.
Cameron replied: 'I don't have anybody I want to drunk dial.'
And Kate seems to feel the same way about her former flames, such as Dancing With the Stars pro Maksim Chmerkovskiy, adding: 'I don't have anyone I want to talk to. They're an ex for a reason...I'm like "okay, and go!". Next!'
Heading home: Cameron, left, Kate, centre, and Leslie Mann looked happy after a screening of The Other Woman
Girls night out: The actresses are helped into a waiting car, with Leslie standing out in a bright red dress
On Wednesday night, all three women dressed up to attend a screening of 'The Other Woman' in Sydney.
Leaving the cinema together, they were seen laughing and joking as they clambered into a waiting black vehicle.
Cameron looked pretty in a floral bomber jacket, paired with a black skirt and bondage style strappy shoes.
Kate covered up a sophisticated black dress with a leather biker jacket, teamed with pointy stilettos.
And Leslie added a dash of colour to the outing, in a bright red, floaty, strapless dress with corseted detailing on the side and on the front of her intricate black heels.
Woman in black: The Sports Illustrated model wore an all black ensemble for her cinema trip
Tied up: Leslie looks gorgeous in a red corseted dress, leaving her blonde hair loose and wavy
Close: The three women have spoken about how much they enjoy each other's company
The three women first caused mass hysteria at Sydney airport on Tuesday when they touched down after a flight from Los Angeles.
But Cameron, Leslie and Kate had no time to soak in Sydney's sights.
The girls attended a photo call for The Other Woman just hours after stepping off the plane, looking quite ethereal in their white garbs.
Glowing: Kate Upton, left, Cameron Diaz, centre, and Leslie Mann, right, posed for photos near the Sydney Royal Opera House on Tuesday
Best friends: It was clear how close Cameron and Kate have become since working together on The Other Woman
