Barker, who won the belt in a points win over Daniel Geale in August, will face Sturm in Stuttgart on December 7.
German Sturm has a strong record against British fighters having drawn with Martin Murray and beaten Matthew Macklin on points.
Considering the controversial nature of the Macklin result, promoter Eddie Hearn confirmed that there is a rematch clause in London should Barker lose.
"We have been in discussions with Felix Sturm's team since the Daniel Geale fight, and with purse bids approaching they made their intentions quite clear," said Hearn.
"Felix is the fight we want both financially and from a legacy perspective and once we were able to introduce our necessary demands, which included a potential second fight in the UK and neutral officials, then this was an opportunity Darren could not turn down."
Should he win the bout against his mandatory challenger Sturm, Barker confirmed that he’d like to face Murray in a domestic super-fight.
"A lot of people don't understand that I have a mandatory defence first but I'd love a big domestic British fight against Murray," Barker told Sky Sports' website.