Background: The Assessment Scale for Positive Character Traits-Developmental Disabilities (ASPeCT-DD) was designed to measure the presence and strength of selected positive or strength-based traits in persons with developmental disabilities. These traits may help to determine level of happiness or value associated with the more commonly measured external indicators of quality of life. Method: The present study examines the psychometric properties of this scale by exploring the factor structure, test-retest and split-half reliability, and inter-rater reliability measures. Also presented is an analysis of descriminant and convergent validity. Results: Results indicate a four-factor solution, with poor to moderate correlation among the factors. Test-retest reliability and measures of internal consistency were in the fair to excellent range, and inter-rater reliability measures were good. Initial evaluation of validation is encouraging. Discussion: Limitations of this study are discussed, as are related opportunities for future research endeavours.