The close-up shot was of the pair's fingers linking, making a pinky promise. The picture was to help make a stand against climate change.
WATCH: Get Salma Hayek's Oscar look by recreating it in simple steps
In the caption, Salma wrote: "It is in my maternal instinct to dream for my children the best future I can possibly give them, but with the worsening of environmental conditions, I worry what kind of world my children and my grandchildren will inherit.
"Stand with me in the fight against climate change. Let’s make a pinky promise to our children to do our best for the environment and #VoteLikeAMadre November 3rd."
Salma Hayek shared a sweet photo featuring her daughter Valentina
The Frida actress also used her platform to pass on the message to her famous friends, and tagged Jennifer Lopez and Eva Mendes to follow suit and make a difference.
The Hollywood star shares Valentina with Francois-Henri Pinault, and the family have been enjoying a holiday in Greece over the past few weeks.
Salma with Valentina and husband Francois-Henri
The actress has been sharing plenty of snapshots from their getaway, including an incredible picture of herself eating breakfast in her bikini in the idyllic setting.
While Salma prefers to keep Valentina out of the public eye, she opened up about the pre-teen during an interview with Town & Country in 2019.
The star described her only child as "very creative, very smart, very funny and very willful."
Salma has described Valentina as "creative and smart"
The mother-of-one also previously gave an insight into Valentina's personality after revealing on Ellen that aged nine, she had started selling slime at her school. However, the venture was soon put to an end after Salma and her husband felt it wasn't right.
Salma is also stepmum to Francois-Henri's children Augustin, Mathilde and Francois. On her husband, the star told Town & Country: "[He] is the best husband in the world. I get to be who I am with him, and I don't feel that somebody tries to limit me."
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