Objective: Health information, including the labelling, must be presented in a manner that is easily understandable to consumers. In recent years, the European Union and the United States have introduced standards for providing health information in a way that is easy for consumers to understand. The Clear Communication Index (CCI) published by the Centers for Disease Control and Prevention (CDC) is a useful tool for this purpose. Unfortunately, there is no such tool in Japan. Therefore, focusing on the package labelling of foods with functional claims (FFCs) sold in Japan, we constructed a Functional Clear Communication Index (F-CCI) and evaluated the FFCs.Methods: The F-CCI was developed by six people, including university staff with pharmacist qualifications and public health experts, by referring to the CDC CCI. The evaluation of FFCs using the F-CCI was performed using the Delphi method, which is one of the formal consensus-building methods in the field of health and medical information. The evaluation was conducted by three qualified pharmacists on five FFC products, and the degree of internal agreement among the evaluators was calculated using Fleiss’ κ.Results: The F-CCI consisted of 18 items that assessed the FFC characteristics. After assessing the labelling of FFCs using the F-CCI, the scores of all the materials ranged between 70 and 80% on the F-CCI, and none achieved 90%, which was considered the acceptable standard (overall κ value_ 0.865). Moreover, it was clear that the ‘readability’ and ‘understandability’ of the labelling were inadequate.Conclusion: The F-CCI developed in this study for the objective evaluation of the labelling of FFC products will act as a tool that will subsequently lead to the proper understanding and use of FFCs by consumers. Further efforts are needed to build and disseminate such tools and user-friendly ways of providing relevant information.