The group had said in June that Stefan Heidenreich, 55, who has been CEO since 2012, would step down at the end of 2019 or earlier, depending on when a successor was chosen.
At that time, De Loecker, a 51-year-old from Belgium, was named deputy CEO and put in charge of Beiersdorf's strategy.
De Loecker joined the company in 2012 as senior vice president Near East from British retailer Tesco , although he spent most of his career at food company Nestle, including in Switzerland, Germany and Russia.
Beiersdorf Chairman Reinhard Poellath said De Loecker was right for the job due to his focus on "growth and renewal".
"The supervisory board strongly supports the proposed concentration on consumers and consumer benefits, skin care, digitalisation, internationalisation, and sustainable growth," he said in a statement.
Heidenreich took over as CEO at a time when when Beiersdorf was losing market share to rivals like L'Oreal and profit margins were falling.
Under his leadership, the group has regained market share, introduced a new Nivea logo as part of his Blue Agenda strategy, focused on emerging markets and stripped out underperforming product lines, with premium products driving recent growth.
There has been media speculation that Heidenreich's departure might have been driven by a disagreement with the company's major shareholder over expansion into premium markets.
Beiersdorf has been extending the Blue Agenda strategy to seek to make its other businesses like La Prairie premium skin cream as strong as its Nivea products.
The Herz family controls Beiersdorf via its Maxingvest holding. Herz is co-owner of the coffee chain Tchibo, which owns a 51 percent stake in Beiersdorf.
Beiersdorf is due to report third-quarter sales on Oct. 30.
(Reporting by Emma Thomasson; editing by Thomas Seythal and Jane Merriman)