<p>Multimodal AI models are increasingly used in clinical decision support systems, but fairness appears to be rarely measured. In this systematic review, our aim was to assess studies that examine fairness in multimodal AI-based clinical decision support (CDS) systems. CDS systems that are rule-based or knowledge-based are considered out of scope. Two searches were used to identify literature focused on evaluating fairness in multimodal CDS systems and to determine the rate at which fairness is included in studies for two focus areas—chest x-rays and sepsis. The review was registered with PROSPERO (CRD42024579923). From 3059 search results, 160 articles included fairness evaluations, 11% (18/160) used multimodal data, and 29 different fairness measurement techniques were used. From 1422 search results related to the two focus areas, 88 studies using multimodal data for CDS related to chest x-ray and sepsis were included. Fairness evaluations were found in 8% (7 of 88) of these, despite 83% (74 of 88) including data on sensitive attributes that could have enabled fairness evaluation. The results show that fairness evaluations are uncommon for studies in multimodal CDS systems. AI-based multimodal CDS systems research would benefit from guidance and tools that support fairness evaluations.</p>