A reliable autism spectrum disorder (ASD) diagnosis can occur as early as 18 months; however, the average age at diagnosis in the United States is over 2 years later. While there are numerous well-known barriers to seeking an ASD diagnosis, no research has examined if separation between a child's biological parents affects timing of ASD diagnosis for their child. Data for this study were obtained from 561 children (M age = 5.4 years, SD = 3.9 years) referred to an urban, outpatient ASD specialty clinic for their first ASD evaluation. Biological parents self-reported their relationship status during the evaluation, which was then categorized as either "together" (married or living together but not married) or "not together" (separated, divorced, or never married). An inverse-probability of exposure weighted linear regression model, which adjusted for 16 different child, family, and sociodemographic variables, was utilized to assess differences in child age of ASD diagnosis between groups. At the time of diagnosis, most children's biological parents were together (69%) versus not together (31%). In the fully adjusted model, children of parents who were together were diagnosed 1.4 years earlier than those who were not together (p < 0.001). Strategies for supporting these families and reducing age disparities are indicated.