The 48-year-old will succeed her party colleague Peter Müller, who in January announced his retirement from top-level politics.
Though her election was not unexpected, Kramp-Karrenbauer will have quite a task keeping the coalition held together. Though German media has criticized her as dull, she has been praised for her tours through Saarland in which she listens to local citizens' complaints.
Kramp-Karrenbauer had to go through two rounds of voting by members of the state parliament to get the required majority. The centre-left Social Democratic Party (SPD) put up stiff opposition to Kramp-Karrenbauer during the first round of voting with its own candidate, Heiko Maas.
Saarland is governed by an unusual coalition of the CDU, the pro-business Free Democrats (FDP) and the environmentalist Greens.
Kramp-Karrenbauer has served in numerous high posts in the state government, including stints as education and interior minister.