High-quality testbed services play a key role in the development and testing of new innovations for health care. To ensure that the development and testing process is valid and reliable, the testbed itself should fulfil a certain maturity level. The objectives of this study were to develop and pilot a new maturity assessment instrument for health care testbeds and to assess the maturity level of participating testbeds using self-assessment auditing. The data were collected in 2022 from 11 health care testbeds in Finland using the developed Health Care Testbed Maturity Assessment (HCTM) instrument in the form of auditing. The data were analysed using descriptive statistical analysis. According to the study results, the average maturity level of the participating testbeds was 51%. The developed instrument indicated preliminary feasibility for assessing the maturity of health care testbeds. Further development and validation of the instrument are warranted.