This study was conducted to collect validity evidence to support the use of an observation instrument to evaluate the performance of special education teachers (SETs) of students with significant disabilities (SWSD). In the study, a purposive sample of 49 SETs of SWSD, who were appropriately credentialed and experienced, evaluated the content of the Teacher Rating and Assessment Instrument for Teachers of Students with Significant Disabilities (TRAIT-SD) to determine each item's importance for teaching SWSD. To do this, the participants were presented with the 37 items on the current version of the TRAIT-SD and asked to rate the importance of each using a 5-point Likert-type scale that ranged from very important to not important. They were also requested to provide narrative statements about the items and to recommend any relevant changes to the items, or recommend any new items they deemed to be missing from the current instrument. The results of the study showed that all participants, regardless of degree level, experience, or geographical location, rated all items between important and very important, resulting in all items being retained on the instrument. Additional comments resulted in a small number of items being reworded for clarity, and one new item being recommended for a subsequent version of the instrument.