This article explores the role of interoperability in the development of digital public services in Europe, analyzing the effects of an European Union (EU)-level initiative (the European interoperability framework, EIF) and the development of e-Government services on how citizens interact online with public administrations. The EIF is a common EU framework providing guidance on public sector interoperability. EU countries are not mandated to follow the EIF, but they are encouraged to take up its guidance in their respective national interoperability frameworks (NIFs). Against this background, this article tests two hypotheses: (a) the introduction of NIFs facilitates the online interaction between citizens and public administrations and (b) better e-Government services encourage citizens to interact online with public administrations. Both hypotheses are confirmed by a panel data analysis covering 26 European countries over the period 2012–2019. The analysis relies on a dummy variable reflecting the adoption of NIFs, built by carefully examining official documents of the countries in the scope of the analysis. Based on the empirical results, this article puts forward two main policy recommendations. First, efforts to improve e-Government services across Europe should be intensified in order to support the overarching digital agenda of the EU and increase benefits for European citizens. Second, interoperability should become a central element when designing new digital public services. Therefore, the European Commission could foster a common approach to interoperability of digital public services across the EU by strengthening the governance of interoperability initiatives and encouraging the adoption of specific interoperability requirements.