Background: Assessments of personality constructs increasingly use self-report and structured interview instruments, which allow for a multimethod measurement approach and decrease specific measurement method bias. The aim of this study was to develop a valid and reliable structured interview for assessing the alexithymia construct. Methods: Sixty interview questions were written initially, each with a set of scoring criteria and prompts and probes to elicit information assisting in the scoring of the respondents’ answers. Results: After pilot testing, the number of questions was reduced to 43, which were administered to 136 community participants and 97 psychiatric outpatients. A series of item and scale analyses further reduced the item pool to 24 items. Principal component analysis and confirmatory factor analysis of these 24 items revealed preliminary evidence of a hierarchical, four-factor structure, with four lower factors nested within two higher-order latent factors. This structural configuration resulted in the Toronto Structured Interview for Alexithymia (TSIA) with two domain scales and four facet scales. The TSIA and its six scales demonstrated acceptable levels of interrater, internal, and retest reliability. The TSIA and its scales correlated modestly but significantly with the 20-item Toronto Alexithymia Scale and its three factor scales, providing some support for the concurrent validity of this interview. Conclusion: The TSIA appears to be a promising structured interview for assessing alexithymia.