The Dax gave up its holiday gains on Friday and closed below the 24,000-point mark. The benchmark index ended the week two percent lower at 23,950 points.
The index also fell below the 200-day moving average, which stands at 24,119 points and signals the medium-term trend. This places the Dax in a downward trend.
Earlier, the benchmark had closed with a gain of 1.3 percent on Ascension Day. It was only the second positive trading day in four weeks.
Trading volume remained comparatively low at 50 million shares on Thursday. Investors continue to focus on the situation in Iran, where political progress remains absent.