Our study evaluates whether having an alternate developmental behavioral disorder (DBDs) diagnosis before diagnosis of autism spectrum disorders (ASD) is associated with delays in diagnosis in a nationally representative sample. Data were obtained from the 2011 National Survey of Pathways to Diagnosis and Services, a survey of children aged 6 to 17 years with ASD, developmental delay, or intellectual disability. A total of 1049 children met inclusion criteria for this study. Of these, 799 children were identified as "late" diagnosis if >12 months elapsed between the age parents reported concerns to a provider and age of ASD diagnosis and 250 as "timely" diagnosis if the gap was ≤12 months. Univariate and multivariate logistic regressions were used to look for association between having an alternate DBDs diagnosed before ASD and "timely" versus "late" ASD diagnosis. The mean time elapsed between the age parents reported concerns to a provider and age of ASD diagnosis was 51 months for children with an alternate DBDs diagnosis before receiving ASD diagnosis and 29 months for those diagnosed with alternate DBDs concurrently with ASD. Having alternate DBDs diagnosis before diagnosis with ASD was associated with "late" ASD diagnosis as follows: developmental delay (adjusted odds ratio [aOR,] 3.46; 95% confidence interval [CI], 1.86-6.42; p < 0.001), intellectual disability (aOR, 9.75; 95% CI, 3.0-31.60; p = 0.04), attention-deficit disorder (aOR, 11.07; 95% CI, 3.43-35.71; p < 0.001), depression (aOR, 8.05; 95% CI, 1.07-60.03; p = 0.0495), and behavioral conduct disorder (aOR, 9.9; 95% CI, 3.55-27.62; p < 0.001). These findings highlight the importance of research to improve the early diagnosis of ASD even in the presence of coexisting developmental behavioral disorders.