Capability maturity models have been developed and are widely used within healthcare aiming to assess the degree of digitization of the organization, but empirical assessments of the models themselves has been undertaken infrequently. We present a mixed-method approach to assessing a novel health capability maturity model developed by a state government responsible for the management of 86 health services. The approach was designed to be suitable for system level assessment of services and pooled the wisdom and experience of subject matter experts and key stakeholders using a combination of survey and interviews to test and tune the proposed assessment approach and parameters. We applied the approach to assess the target capability model across a number of public health services in Victoria, Australia. The result showed sufficient validity to be able to generate recommendations for further improvement of the capability model and the assessment approach to enable broader application within Australia.