To establish the association between malocclusion severity and orthodontic case complexity as assessed by the Dental Aesthetic Index (DAI) and the American Board of Orthodontics Discrepancy Index (ABO-DI), respectively.Cross-sectional study.Pre-treatment dental casts and radiographs from 500 individuals (294 women and 206 men; mean age = 26.06 ± 11.58 years) were randomly selected from the orthodontics department of a private university.Malocclusion severity was assessed using DAI and case complexity was evaluated with ABO-DI. Three previously calibrated operators performed the measurements. Spearman's correlation analysis, Mann-Whitney U test, Kruskal-Wallis test and a linear generalised model were used for statistical evaluation (P < 0.05 was considered significant).Although the correlation (r = 0.45; P < 0.0001) between malocclusion severity and case complexity was moderate, strong evidence of an association (P < 0.001) between dichotomised DAI and ABO-DI total scores was observed. The linear generalised model showed that for each point of increase in DAI score, the ABO-DI score increased an average of 0.3624 points (P < 0.0001).An association between malocclusion severity and case complexity is suggested. A linear generalised model could be used to predict the complexity of the case from the malocclusion severity (DAI score).