Born as Elspeth Hallsmith in Cornwall, she was educated privately up to the age of 16, when she decided to take up a job at the War Office. During the Second World War, she volunteered to work on the canals as a boatwoman. Later on, her experiences as a trainee boatwoman on the Grand Union Canal would become the basis for her debut novel, Maidens' Trip.
In September 1946, Smith, still only 23, went off to India with a team of documentary film-makers that included the poet Laurie Lee, who served as the scriptwriter on the team. During the trip, Cider with Rosie, Lee's classic account of growing up in rural Gloucestershire, was in its embryonic stages. Emma Smith was one of those who would later encourage Lee to complete what became one of the best loved accounts of childhood in English literature.
After nine months in India, Smith returned to England in 1947 and set down to write her first book. Maidens' Trip (1948) proved to be a critical and a commercial success and won the John Llewellyn Rhys Prize. With the proceeds from it, she moved to Paris, where she took a room in the Hotel de Tournon and, drawing on her memories of India, typed up her second novel.
The Far Cry was published in 1949 to even greater acclaim and was republished in 2002 by Persephone Books. The tale of a young English girl and her cantankerous father travelling together through India, it was awarded the James Tait Black Memorial Prize for fiction in 1949, and later reissued in a Penguin edition.
In 1951, Smith married. Within the next six years, she became the mother of two children, and then suddenly a widow. Finding herself a single mother, she moved to Radnorshire in rural Wales to raise her children. Her writing now took a back seat to her family duties.
Only very slowly did Smith finally return to writing. She produced several children's books, as well as a novel, The Opportunity of a Lifetime, in 1978. But she never regained the celebrity she had enjoyed in the late 1940s.
The novelist Susan Hill has been instrumental in the recent revival of interest in Emma Smith's works. Many years after The Far Cry had gone out of print, Hill found a copy of the book in a jumble sale. She wrote enthusiastically about her discovery in the Daily Telegraph, and in 2002 – 50 years after the Penguin edition – Persephone Books reprinted The Far Cry as one of a series of forgotten classics by women writers. Hill supplied the afterword to their edition.
Since 1980, Emma Smith has lived in Putney in south-west London.
In 2008, Smith returned to writing with her memoir The Great Western Beach, describing her childhood in Cornwall between the two World Wars. Bloomsbury Publishing, the publishers of The Great Western Beach republished Maidens' Trip in 2009. Due to the success of her first memoir, she was encouraged by Bloomsbury Publishing to write a sequel. This took the form of As Green As Grass, which was published in 2013, and covered Smith's life between 1935, when she left Newquay at the age of 12, to 1951 when she married.