In a new Instagram post, the Call The Midwife star referenced victims who have been displaced after Russian President Vladimir Putin launched an invasion of Ukraine last month.
The actor urged fans to donate to the charity, Disasters Emergency Committee, which brings together "15 leading UK aid charities, raising funds to quickly and effectively respond to overseas disasters".
The Nativity Rocks! star wrote: "On International Women’s Day, let's do something worthwhile for some women who really need our help. Over a million people have fled their homes in Ukraine. They need food, water, shelter and medical assistance.
"The DEC has launched an urgent appeal. @disastersemergencycommittee member charities are on the ground in Ukraine and in bordering countries, bringing vital lifesaving aid to those in need. Please help."
The 39-year-old, who welcomed her second child with partner Jack Ashton in November, is one of many famous names that have been speaking out amid the conflict between Russia and Ukraine.
Earlier in the day, This Morning host Holly Willoughby broke down in tears live on TV for a second day running as she was moved by the plight of children fleeing the warzone.
The mother-of-two became unable to control her emotions as she and Phillip Schofield discussed the story of an unnamed 11-year-old boy who travelled 600 miles across Ukraine alone, with his parent's phone number written on his hand.
Willoughby was unable to speak and was shown sobbing and wiping away tears as Schofield cut to a commercial break.
This came a day after Willoughby and Schofield both became overwhelmed discussing a viral video of a young girl known as Amelia, singing Let It Go in Ukrainian in a bomb shelter.
The 41-year-old, who is the mother of 12-year-old Harry, 10-year-old Belle and seven-year-old Chester, recently confessed on social media she was struggling to explain the Ukraine crisis to her children.
She said: "How do I explain this to my children… I was asked questions last night I didn’t have the answers for…"
Russia has announced it will hold fire and open humanitarian corridors in Ukrainian cities, allowing civilians from Kyiv, Kharkiv, Mariupol, and Sumy to leave and enter Russia and Belarus.
Putin began the invasion of Ukraine on 24 February, prompting thousands of Ukrainians to attempt to flee the country.
Watch: Holly Willoughby in floods of tears again over the plight of Ukrainian children