Russia's central bank alleged that a banker at Deutsche Bank's Russian branch had manipulated markets by conducting 300 billion rubles ($4.87 billion) of trades with relatives over two and a half years.
The central bank said the trades, made between January 2013 and July 2015, had generated a profit of 255 million rubles for Deutsche Bank employee Yuri Khilov and three relatives.
The Russian central bank said it had passed its findings to law enforcement for their assessment of what had happened.
The central bank's investigation was conducted with help from Germany's Federal Financial Supervisory Authority.
It is separate from an investigation into so-called "mirror trades" involving Deutsche's Moscow office which could have allowed clients to move money from one country to another without alerting authorities in 2014.
A Deutsche spokesman said the bank had conducted an internal investigation into the activities of Khilov, who he said was a former Deutsche employee.
Deutsche has provided its findings to the market regulator and will cooperate closely with authorities, the spokesman said.
Khilov did not immediately respond to a message seeking comment.
The Russian central bank's findings are an embarrassment for Germany's flagship lender, which recently cut back its investment banking activities in Russia.
Deutsche is also facing a large penalty in the United States for allegedly misleading investors when selling mortgage-backed securities.
It was not clear whether Deutsche will be fined in Russia over the trades involving Khilov.
The Russian central bank alleged in a statement that Khilov and his relatives had manipulated trading in eight securities on the Moscow Exchange.
Acting on behalf of Deutsche's London branch, Khilov made trades which were favorable to his relatives and in doing so manipulated markets, the statement said.