This study aims to establish whether children of an immigrant maternal population presented with a higher rate of autism than the indigenous population and to explore their presentation with regard to severity of symptoms, demographics and ethnicity. It is a retrospective case note analysis of 366 children who presented to the paediatric developmental service in the Adelaide and Meath incorporating the National Children’s Hospital, Tallaght, Ireland between 2007 and 2009. During the study period, 366 children presented. Fifty-eight children (16 %) had mothers who were born in Africa and 53 (14 %) were born to mothers originating from a wider variety of countries. Two hundred and forty-eight children (68 %) had mothers born in Ireland. Maternal origin was not identified for seven children (2 %). An autistic spectrum disorder (ASD) was diagnosed in 131 children and speech and language delay in 132. Of the children with an ASD diagnosis, a higher proportion of the African cohort 13/18 (72.2 %) presented with moderate/severe cognitive disability compared to the Irish group 9/55(16.3 %), and the children in the African cohort showed a higher heritability with 36.9 % having a positive family history of autism reported compared to 26.3 % of the Irish cohort with an ASD diagnosis. Conclusion: This study highlights an observation of increased rates of ASD among a migrant population derived particularly from children born to mothers originating in Sub-Saharan Africa. This cohort is more severely affected. Further validation in an epidemiological sample is warranted, which if replicated, may help to identify possible aetiological risk factors.