Home24's valuation had been cut to 420 million euros in the funding round that raised 20 million euros ($22.5 million) of new capital.
The previous valuation was 981 million euros, and other investors including Baillie Gifford and Kinnevik.
Home24 made an operating loss of 75.3 million euros in 2015 on sales of 234 million euros. Revenue growth slowed for the company, although the portal managed to narrow losses in the first quarter of 2016.
Rocket announced last week it made a first-half loss of 617 million euros ($691 million) after heavy writedowns on various companies in its portfolio, in particular the Global Fashion Group.
Reuters reports that Rocket Internet was founded in Berlin in 2007 by brothers Oliver, Alexander and Marc Samwer, and has set up 150 startups in 110 countries in an effort to emulate the success of Amazon, China's Alibaba and Uber in new markets.
But the share price has fallen by more than a third this year after the valuation for its Global Fashion Group was dropped by two thirds in April by Rocket's second-biggest shareholder Kinnevik.
The move prompted concerns about the worth of the company’s other holdings.