Background Trichotillomania (TTM) is a psychiatric disorder that leads to significant hair loss, distress, and impairment. Few validated measures exist to assess TTM, and psychometric research examining these tools is sparse. This study evaluated the psychometric properties of commonly used TTM severity measures and extended prior research by including hair loss severity ratings in our analyses. Methods Participants included 91 adults (92.3% Female; M age = 35.0) with TTM who completed baseline assessments as part of a randomized clinical trial of psychotherapy for TTM. TTM measures included the Massachusetts General Hospital Hairpulling Scale (MGH-HS) and National Institute of Mental Health Trichotillomania Severity Scale (NIMH-TSS). Independent evaluators rated photos of participants’ most severely affected pulling sites using a one-item hair loss severity scale. Results Results showed mixed psychometric properties for TTM measures. The MGH-HS showed acceptable internal consistency (alpha = 0.83; omega = 0.89), while the NIMH-TSS had lower internal consistency (alpha = 0.52; omega = 0.73). Both the MGH-HS and NIMH-TSS demonstrated low test-retest reliability. Total scores on the MGH-HS and NIMH-TSS were not associated with hair loss severity. Conclusions Given these findings, it is imperative to develop new, psychometrically-sound TTM measures. These results also emphasize the importance of a multi-method approach to TTM assessment. In addition to self-report and clinician-administered measures, hair loss severity ratings may offer valuable information as part of a comprehensive assessment of TTM.