The portrait was shared through the family's official social media channels, alongside a message which read: 'To mark HRH The Duchess of Cornwall's 70th Birthday, we are releasing this new portrait, taken by Mario Testino.'
'The image was taken in the Garden Room in Clarence House in May.'
The photograph shows the couple looking happy and relaxed, dressed in coordinating smart navy blue outfits as they smile for the renowned photographer.
Fans of the pair have taken to Instagram to compliment the snap, with one writing: 'What a Lovely portrait. Happy Birthday,' and a second agreeing: 'Lovely photograph... Camilla looks amazing for her age.'
Ahead of her birthday, which is on 17th July, Camilla has also given an intimate insight into her life since marrying Charles, whom she wed in April 2005 after the death of his first wife and mother of his two sons, Princess Diana.
Camilla herself has two children from her first marriage to Andrew Parker Bowles: Tom, born in 1974, and Laura, born in 1978, both of whom now have daughters of their own.
'Children keep you young,' she told the Daily Mail earlier this year. 'I have my grandchildren quite a lot. They are charging about all over the place. You can't just sit down and say: "Sorry, I'm too old, I can't play."
'Sometimes, when we are with my husband in Scotland, [Charles] reads them Harry Potter. And he does all the voices, because he is a brilliant mimic. I'm not very good. I try to do the voices, but acting isn't my forte. But he sits down and they all sit with him.
'It's really sweet. He's extremely good with children. They love it.'
However, despite spending time with both her own grandchildren and step-grandchildren Prince George and Princess Charlotte, Camilla admitted that she has recently become more aware of her age.
'You know, there was a lady in a crowd the other day. She said: "I'm your twin, I'm going to be 70 on the same day as you. I've been told by a friend that we are officially old."'
'And I thought: "Oh dear." I'm not sure about being officially old. The trouble is that I don't feel it in my head. Sometimes I still feel a teenager, but then other bits of your body don't quite agree.
'When your feet are screaming in agony at the end of the day, I realise that perhaps, you know, I am getting older.'