Background and Objective: The Covid-19 pandemic showed how crucial digital public health (DiPH) interventions are for continuous treatment and system sustainability. Several studies highlighted how the digital system transformation might improve access to and quality of healthcare services. However, there is no consensus on how to best assess the national readiness for the digitalization of such systems. Therefore, this Delphi study aimed to collect indicators to measure the maturity of DiPH systems nationally. Methods: The three-stage international and interdisciplinary Delphi study included 82 participants. During the first round, participants were invited to propose indicators to measure maturity among the technological and legal requirements of DiPH tools, the willingness of the general public to use them, and the degree of application of DiPH tools to the national healthcare system. The suggestions were qualitatively assessed and presented for ranking on a 4-point Likert scale during the second round. Experts were also able to rephrase or add indicators. In the third round, experts could only rank indicators. Results: 106 indicators to measure the maturity of DiPH systems were included. Of these, 33 fall under the legal and 30 under the technological requirements. 27 assess the social level and 16 the degree of application. All dimensions can be clustered further into 3-4 sub-groups each. The qualitative analysis pointed to the importance of data protection regulations, affordable access to smartphones and the internet, interoperability between interventions, financial incentives, user motivation and literacy, and whether interventions were implemented as local pilots or national system services. Conclusions: The study identified indicators for interdisciplinary assessing DiPH system maturity. While this Delphi can’t answer how best to integrate these indicators into national health system evaluation procedures, this approach is an essential first step towards an index to measure the maturity of DiPH systems.