Markus Reubi studied law at the University of St. Gallen and holds an Executive Master of Business Administration from McGill University and HEC Montreal. Following various roles in the private sector, including in management consultancy, he joined the Swiss Confederation's diplomatic service in 2003, initially working at the head office in Bern, before being posted to Algeria and China. From 2014 to 2018 he was responsible for setting up the Swiss Business Hub (for export and investment promotion) in Canada. From 2018 to 2022 he was deputy head of mission at the Swiss representation in Tokyo, where he was responsible for diplomatic tasks and coordinating implementation of the Federal Council's foreign policy strategy – with its thematic focus areas of peace and security, prosperity, sustainability and digitalisation – with Japan, which is one of the eight priority countries of Switzerland's foreign policy.

Since 1 July 2022, Markus Reubi has overseen a cross-disciplinary approach to current challenges in his role as deputy head of the Prosperity and Sustainability Division (PSD). The PSD is a division within the FDFA State Secretariat that supports the Federal Council in linking thematic policy areas with foreign policy. It ensures the coherence of positions and efficient cooperation and coordination between the FDFA and relevant offices in other departments. This coordination work focuses primarily on the areas of economics and finance, energy, the environment and health, as well as education, science, transport and space.

Through its decision of 14 December 2018 on the new organisational structure for the 2030 Agenda, the Federal Council created two delegate positions within the DETEC and the FDFA, who will take it in turns to chair the 2030 Agenda Steering Committee every two years.  On 29 June 2022, the Federal Council appointed Markus Reubi as delegate of the Federal Council for the 2030 Agenda.