The value of alexithymia assessments in medical and psychiatric research is well documented, but such assessments in cannabis abusers are scarce. Moreover, despite repeated calls for multimethod alexithymia evaluations, researchers typically use 1 self-report only: the 20-item Toronto Alexithymia Scale. Herein, we evaluated (1) the psychometric properties of the Observer Alexithymia Scale (OAS), (2) the correspondence between 3 alexithymia measures, (3) OAS raters' affect and its relationship to OAS scores, and (4) cannabis abusers' alexithymic features. Eighty-seven cannabis abusers completed self-reports measuring alexithymia (Toronto Alexithymia Scale, Bermond-Vorst Alexithymia Questionnaire-B), depression (13-item Beck Depression Inventory), and anxiety (State and Trait Anxiety Inventory-Form Y) and asked relatives to rate them using the OAS. The raters also completed the self-report scales. The OAS met acceptable reliability and validity standards, with the exception of relatively low interrater reliability for one of its subscales. Rater affect appeared to influence OAS scores, albeit slightly. Patients' OAS scores were higher than scores reported for people-in-general samples and lower than those for outpatient clinical samples. Alexithymia rates were similar to those previously reported in cannabis abusers. Our results demonstrated the adequacy and appropriateness of the OAS in these (and related) clinical samples, which may encourage multimethod alexithymia assessments in both research and clinical practice.