Background: The association between parental socio-economic status (SES) and autism spectrum disorders (ASD) has been studied in several countries, but the results have been contradictory. Aims: The aim of this study was to examine the association between maternal SES and subtypes of ASD in Finland. Methods: A national case–control study was conducted. Children born in 1991–2005 and diagnosed with ASD by the year 2007 were identified from the Finnish Hospital Discharge Register (FHDR). Their matched controls were selected from the Finnish Medical Birth Register (FMBR). There were 3468 cases and 13,868 controls. The information on maternal SES was collected from the FMBR and categorized into upper white-collar workers (referent), lower white-collar workers, blue-collar workers and “others”, consisting of students, housewives and other groups with unknown SES. The statistical test used was conditional logistic regression. Results: The likelihood of ASD was increased among offspring of mothers who belong to the group “others” (adjusted OR = 1.2, 95% CI 1.009–1.3). The likelihood of Asperger's syndrome was decreased among offspring of lower white-collar workers (adjusted OR = 0.8, 95% CI 0.6–0.9) and blue-collar workers (adjusted OR = 0.6, 95% CI 0.5–0.7). The likelihood of pervasive developmental disorder not otherwise specified (PDD-NOS) was increased among offspring of blue-collar workers (adjusted OR = 1.5, 1.2–1.9) and “others” (adjusted OR = 1.3, 1.1–1.7). No association was found between maternal SES and childhood autism. Conclusions: The association between maternal SES and ASD differs by ASD subtype. Socio-economic groups might differ from each other by risk factors for ASD subtypes or by their service use.