It is known that offenders with immigrant backgrounds are over-represented in criminal as well as forensic psychiatric populations and that the prevalence of dyslexia among prisoners with Swedish as a native language is much higher than in the general population in Sweden. The aim of this study was to diagnose dyslexia in a sample of 23 male offenders with immigrant backgrounds undergoing a forensic psychiatric investigation with the objective to discuss the appropriateness of a commonly used assessment procedure in accordance with DSM-IV. Dyslexia was diagnosed individually; the participants took reading and writing tests, as well as intelligence and neuropsychological tests. Nine out of 23 participants (39%) were diagnosed as having dyslexia. Thus, dyslexia seems to be common among male offenders with immigrant backgrounds undergoing FPI, and for that reason it is important to investigate their reading and writing abilities. Dyslexia is regarded as a functional impairment in Sweden, and therefore all offenders with dyslexia undergoing a forensic psychiatric investigation, irrespective of their background, should receive help with the legal procedure, for example their crime files and police investigation documents should be read to them. We conclude that in addition to the criteria in DSM-IV the assessment procedure should be extended with phonological tests.