The Scottish singer -- whose 2009 Britain's Got Talent performance of "I Dreamed a Dream" led to a singing career and a memoir -- told The Observer over the weekend that she recently sought the help of a specialist.
"Nobody told me to. I thought I had a more serious illness and couldn't function properly," she said.
Boyle said that she performed well on intelligence tests, but the doctor diagnosed her with Asperger's, a developmental disorder that often impacts social skills and ability to read emotions.
"Now I have a clearer understanding of what's wrong and I feel relieved and a bit more relaxed about myself," the 52-year-old said.