Nikki Adler then completed an education at Deutsche Post AG alongside her amateur career.

In May 2013, with a victory over Zane Brige from Latvia, the second World Championship title followed, this time after the WBF version.

She won the WBC title in November 2013 in a fight against Zane Brige over 10 rounds after unanimous decision in Grozny.

In May 2014, Nikki Adler defended her WIBA title in Krasnodar, Russia against Gifty Amanua Ankrah.

In 2015 Adler focused on the defense of her WBC title in a gripping battle against Szilvia Szabados in the MHPArena Ludwigsburg.

Adler defeated the Georgian in Saarbrücken in July 2016 by knockout and remains the reigning and undefeated world champion in the super middleweight division.