Background: Content validity is a key measurement property that should be considered when selecting or reviewing a patient-reported outcome measure (PROM). In the field of communication disorders, there are several PROMs available, most of which are disease specific. It is unknown what the quality of the content validity of these PROMs is. Aims: This study aimed to evaluate the content validity of existing communication PROMs used with adults with communication disorders. Methods: This study evaluated PROMs drawn from a previously published systematic literature review. Of 31 measures, 25 measures were included in this review, covering a range of communication-related constructs in different communication disorders. The process of rating followed the COnsensus-based Standards for the selection of health Measurement INstruments (COSMIN) methodology for assessing the content validity of PROMs. There were three stages to the evaluation process comprising Step 1: evaluating the quality of the PROM development, Step 2: evaluating the quality of content validity studies on the PROM (if available) and Step 3: evaluating the content validity of the PROM overall, based on the quality and results of the available studies and the PROM itself. Main Contribution--Step 1: With regards to the quality of the PROM development, 21 of 25 PROMs were rated as inadequate. Step 2: Content validity studies were available for five of the PROMs. All of these studies were rated doubtful or inadequate. Step 3: The quality of the available evidence on content validity of the included PROMs was overall very low. Only the evidence on the content validity of the Communication Participation Item Bank (CPIB) and the Neuro-QoL (Quality of Life in Neurological Disorders) was rated as of moderate quality. Conclusions: Results of this study highlight the scarcity of high-quality evidence on the development and content validity of PROMs that aim to capture the construct of communication. This review is a call to action for future PROMs to include both the target population and professionals in development and content validity testing, using rigorous methodology in the process.