Researchers fear that misdiagnosis could be a contributory factor in anti-social and criminal behaviour later in the life.
Lindsay Peer, the education director at the British Dyslexia Association, said many children struggling to learn English as an additional language are also dyslexic. Yet they are not getting the support they need because teachers are attributing their difficulties to simply having to learn English.
She believes thousands of children are missing out on the now well-established teaching methods which could help them overcome their problems in processing language.
And she fears the added difficulties of learning a second language could mean there are higher rates of dyslexia among such children - perhaps as high as 15 per cent.
Around 4 per cent of an average population can be expected to have severe dyslexia, with up to another 6 per cent having moderate or mild problems.
Last year, a London-based charity found that more than half of a random sample of prisoners were dyslexic.
Ms Peer said: "Around 10 per cent of any population is dyslexic, yet often the condition goes unrecognised, especially among ethnic-minority communities.
"Problems with reading, writing or spelling can be misdiagnosed and put down to the fact that English is a second language," she said.
Because of their dyslexia, many pupils may be having problems in learning their mother tongue as well. But conventional additional support will be a waste of time - unless it is made dyslexia-friendly.
Ms Peer wants to see all second-language teachers to be trained in diagnosing dyslexia and the appropriate teaching methods for pupils with the problem.
The Department for Education and Employment is funding a review of the research literature on dyslexia and multilingualism, the results of which are due out this autumn.