The Blue Book Of Nebo is the first-ever translated book to win a Yoto Carnegie medal for writing in the almost 90-year history of the awards.
Celebrating children's authors and novelists who write young adult fiction, the award is unique in that it is judged solely by librarians.
The Blue Book Of Nebo explores Welsh identity and culture and is told through the lens of a mother and son who live in the post-apocalyptic world of Nebo.
Manon Steffan Ros, who wrote and translated the book, said that growing up with the Welsh language was a "privilege" and something that had always brought her "joy".
Discussing what it was like to win the award, she said: "I used to see the word Carnegie on the covers of my favourite books as a child and the fact that The Blue Book Of Nebo now has that honour bestowed upon it means more than I can say - and to be the first book in translation to win the Yoto Carnegie Medal for Writing is a source of great delight.
"One of the greatest privileges of my life has been the fact that I was raised through the medium of the Welsh language, and having to access two languages has brought me so much joy and opportunity.
"There's a huge, lively, thriving Welsh language and cultural scene that I'm honoured to be a part of.
"Each language offers a unique and enriching perspective on the world, and so literature in translation has the potential to enhance our lives greatly.
"Your favourite book might not yet be translated into a language that you understand."
The Yoto Carnegie Awards also include a medal for illustration, which was won by Saving Sorya: Chang And The Sun Bear by Jeet Zdung.
Zdung dreamed of drawing cartoons as a child growing up in Vietnam and said that the process of creating the book "was a journey to satisfy the child's longing" he had to create an immersive movie on paper using influences of comics and manga.
Talking about what it was like to win the award, he said: "Together with Trang Nguyen, we hope these books will contribute to the conservation of wildlife by sharing with the readers what we know, what we love and care about.
"For me, this is a long and enduring journey.
"Winning the Yoto Carnegie Medal for Illustration is a great honour.
"We hope that the impact of the prize will be felt widely and draw attention to the plight of the Sun Bears and other wildlife."
The Blue Book Of Nebo and Saving Sorya: Chang And The Sun Bear were selected from a shortlist of several titles and were praised by judges for providing an "immersive" experience for readers.
The original Welsh publication of The Blue Book Of Nebo, Llyfr Glas Nebo, has won multiple awards including the 2019 Wales Book Of The Year.