Aims: Few tools are available to assess the communication skills of adults with severe and multiple disabilities functioning at unintentional to early symbolic levels. An exception is the Triple C: Checklist of Communicative Competencies. In this study, aspects of support worker and clinician agreement, internal consistency and construct validity of a revised version of the Triple C were explored. Method: Triple C checklists were completed for 72 adults with severe intellectual disabilities (ID) by 118 support workers and stages were assigned by the researchers. Two support workers completed checklists for each of 68 adults with ID. Three researchers also conducted direct observations of 20 adults with ID. Results: The average support worker agreement for items across the five stages of the Triple C ranged from 81% to 87%; agreement for stage assignment based on first and second support worker checklists was moderate to high (k = 0.63). Internal consistency was high KR20 = 0.97); the stages were found to tap one factor (accounting for [similar to]74% of variance), interpreted to be unintentional to early symbolic communication. Agreements between stages based on researcher observations and support worker-completed checklists were 35% and 71% across first and second support workers. Conclusion: The revised Triple C provides a reliable means of gathering data on which to determine the communication skills of adults with severe and multiple disabilities. The results support a collaborative use of the Triple C, such that a speech-language pathologist or other communication specialist works with a support worker to ensure understanding of the skills observed and development of appropriate intervention strategies.