Digital transformation approaches outside the public sector are changing citizens' expectations of governments' ability to deliver high-value, real-time digital services. In response to the changing expectations and triggered by supranational agreements, governments are changing their mode of operation to improve public service delivery, be more efficient and effective in their designs, and achieve objectives such as increased transparency, interoperability, or citizen satisfaction. However, beyond the availability of consultancy reports, there is little systematic insight into the way that public administrators themselves are currently defining digital transformation in their own day-to-day practices, how they are approaching digital transformation projects, and what their expected outcomes are. We provide an empirically-based definition of digital transformation derived from expert interviews and develop a conceptual framework with reasons for, processes to, and expected outcomes of digital transformation in the public sector. •Empirically grounded definition of digital transformation focuses on holistic process to change products and culture.•Digital transformation goes beyond digitization and digitalization by including the whole organization.•Digital transformation changes bureaucratic and organizational culture and relationships to stakeholders.•Short-term output focus on measurable increases in new digital services.•Long-term impact and outcome focus on increases effectiveness and citizen satisfaction.