But he never picked up the medals he earned for his service.
Now, 73 years after the war ended, his family has finally received his medals from the Ministry of Defence.
Dahl's grandson Ned Donovan told BBC News they arrived on Wednesday - the 80th birthday of the late author's widow Felicity.
He presented them to his step-grandmother as a surprise at her party.
"She was extremely thrilled and said she was going to put them under her pillow," Donovan said.
While in the RAF, Dahl was badly injured when his plane crashed in North Africa in September 1940. He spent six months in hospital in Egypt.
He then rejoined his squadron in Greece and took part in The Battle of Athens in 1941.
The medals are the 1939-1945 Star, which is given to those who served overseas during World War Two; the Africa Star, for those who served in North Africa between 1940-43; the Defence Medal, awarded for non-operational service; and the War Medal, awarded to all full-time armed forces personnel.
Donovan said it was typical of his grandfather not to have picked them up at the time.
"It's very him for him not to have collected his medals - he'd have thought it was terribly uncool!
"He crashed his plane, blinded himself and then started flying again. He signed up the first day and got right into it."
73 years late and 28 years after his death, my grandfather Roald’s World War II medals arrived in the post yesterday from the MoD. He never collected them at the time thanks to a bureaucratic mix-up. And so last night I gave them to my step-grandmother as a surprise. pic.twitter.com/nkyq9nZwz5— Ned Donovan (@Ned_Donovan) December 13, 2018
A Ministry of Defence Medal Office spokesperson said Dahl hadn't been automatically issued with the medals because he left the RAF before the medal criteria were published, meaning he would have needed to apply for them.
Donovan said he would like the medals to go on display at The Roald Dahl Museum and Story Centre in Great Missenden, Buckinghamshire.
He began wondering about his grandfather's medals a couple of years ago, he said.
"We have a museum, I remember talking to the archivist there... they didn't have them, so I asked my family, my mum, aunt, grandmother, siblings. They'd never seen them.
"I got hold of his service records form the Ministry of Defence - he was such a good storyteller, you were never sure what was true!"
After writing to the medals office at the MoD, he and his step-grandmother signed the relevant forms but didn't hear anything back until the medals arrived in the post.
The MoD spokesperson said: "The Medal Office is delighted to hear that the medals belonging to Roald Dahl have been reunited with his family.
"We are indebted to Roald Dahl, who served as an RAF pilot in World War Two, and to all those who have served our country."
Dahl wrote about his experiences in the RAF in his book Going Solo. Later, after a posting to Washington, he supplied intelligence to the British security services.