Deutsche Bank's chief Josef Ackermann has warned in a TV interview that the international credit crisis will hurt its latest three month results.
He admitted Deutsche Bank "made errors during this crisis" during an interview on ZDF Television.
Deutsche Bank shares closed 2.9% lower, the second biggest faller on the Dax.
Mr Ackermann did not say how much the crisis would cost, but warned he would probably not go ahead with plans to hire an extra 4,000 staff this year.
He said that 29bn euros ($41bn; £20bn) worth of credit agreements for big acquisitions have to be reconsidered.
German banks have been among the worst hit by exposure to debt backed by sub-prime mortgages from the US.
Sub-prime mortgages are offered to people with low incomes or inferior credit records.
Two German banks, IKB and SachsenLB, had to be bailed out because they held too much of such debt.
Last month, Deutsche Bank was one of the banks that borrowed money directly from the US Federal Reserve at a newly lowered rate designed to help institutions that were short of liquidity.