The current CDU secretary general received 51 percent of the vote from delegates at the party conference in Hamburg in a second-round runoff against main rival, Friedrich Merz. The third candidate Jens Spahn was eliminated in the first round.
Merkel will remain Germany's chancellor.
Addressing delegates ahead of the vote, Kramp-Karrenbauer spoke of perceptions that she was a "mini-Merkel," saying: "People consider me a copy, just more of the same, but I can tell you that I stand here as my own person, as myself."
Kramp-Karrenbauer, who served as state premier of Saarland between 2011 and 2018, was Merkel's favored successor. She has served as the CDU's secretary general since February.
A new leader for the 'last unicorn'
In her speech to the delegates before the vote, Kramp-Karrenbauer sought to hit positive notes. She recalled joining the CDU in the 1980s because the party was, in her eyes, the only one that offered a centrist alternative to doomsday scenarios like nuclear war.
It was "the party that didn't see everything pessimistically" and "that draw people from all political realms into the middle"
The implication was that with her at the helm, the CDU would be a moderate force capable of negotiating challenges like the rise of far-right populism and resurgent nationalism.
While acknowledging that the party was going through a trough in public opinion polls, Kramp-Karrenbauer argued that the CDU's dip was far less drastic than other conservative parties around the world. She even went so far as to call the Christian Democrats the "last unicorn in Europe."
This vaguely surreal image was in keeping with a speech that was perhaps a bit general at times but was surprising passionate for a self-proclaimed moderate who envisioned a party that "had the better ideas" rather than "attacking opponents most sharply."
One final victory for Merkel
The big winner on the day, other than AKK of course, was Angela Merkel. Not only did Kramp-Karrenbauer run her campaign for the party chair by promising a large measure of continuity.
Significantly, when arguing that CDU had to remain a big-tent association of the center, she turned to "Angela" to acknowledge the role of the chancellor and former party chairwoman of eighteen years in moving the conservatives into the middle.
Kramp-Karrenbauer's election is essentially an endorsement, if not a particularly ringing one, for a centrist course and more diverse party than the return to conservative fundamentals offered by Merz. His cause was perhaps hurt by a rather impersonal speech that got off to a slow start, although he almost pulled off an astonishing comeback.
Notwithstanding statements by all parties to contrary, it would have been difficult to imagine Merkel seeing out her last term as chancellor until 2021, if a fierce critic like Merz had led her own party. With her protégée and ally AKK occupying that position, Merkel's political end is far more likely to be gradual and harmonious.