Between 2012 and 2014, Rehlinger was state minister of justice, consumer protection and environmental affairs in the government of the minister-president of Saarland Annegret Kramp-Karrenbauer.

In 2014, she succeeded Heiko Maas as deputy minister-president and state minister for economic affairs, first under the leadership of Kramp-Karrenbauer (2014–2018) and later Tobias Hans (2018–2022).

[6] In the negotiations to form a coalition government on the national level following the 2017 federal elections, Rehlinger co-chaired the working group on agriculture.

At a SPD national convention in 2019, Rehlinger, with Klara Geywitz, Hubertus Heil, Kevin Kühnert and Serpil Midyatli, was elected as one of the five deputies of the party's co-chairs Saskia Esken and Norbert Walter-Borjans.

[8] Rehlinger was nominated by her party as delegate to the Federal Convention for the purpose of electing the president of Germany in 2022.

[9] In October 2023, Rehlinger joined the first joint cabinet retreat of the German and French governments in Hamburg, chaired by Chancellor Olaf Scholz and President Emmanuel Macron.