The Agatha Christie: A Life in Photographs exhibition runs at National Museum Cardiff from Saturday until 3 September.
It shines a light on her family life, marriages and international adventures.
The queen of crime's grandson Mathew Pritchard said relatives were "delighted" to share the pictures.
Director general of the museum, David Anderson, said: "This is a beautifully curated exhibition which gives us an insight of Agatha Chirstie's life in photographs.
"The vivid images, accompanied by quotes in her own words, convey her humour and intelligence, as well as her love of travel and adventure. I hope our visitors enjoy a look into the extraordinary life of the most-widely published author of all time."
Each image is accompanied by a quote in Christie's own words, drawn from both published works and unpublished personal correspondence, capturing her thoughts and feelings.
In one, she says: "Nothing has surprised me more in life than to have become a famous authoress - I sometimes can't believe it's really me".
Family photos show Christie as an energetic and adventurous young woman, with photographs of her surfing on an idyllic Muizenberg beach in South Africa and roller-skating on Torquay pier.
A timeline will also mark the key milestones in her life, including the first performance of the world's longest-running play, The Mousetrap, and the publication of her seminal works, such as Murder on the Orient Express and And Then There Were None.
Chtistie, a crime novelist, short story writer and playwright, is best known for 66 novels and short story collections.
She is widely cited as the best-selling author of fiction of all time, with an estimated two billion sales worldwide.
Photographs from the private collection of legendary crime author Agatha Christie are to be displayed in Cardiff.