The Wall Street Journal reported last week that the two companies are in talks for a potential deal. Icahn, along with shareholder Darwin Deason, said Monday they don't trust Jacobson to lead the potential negotiations.
"He is neither qualified nor capable of successfully running this company, let alone negotiating a major strategic transaction that will do more than save his own job," Icahn and Darwin wrote in a letter to Xerox's board of directors.
The investors, who hold a combined 15 percent stake in Xerox, are looking to put four new members on the company's board.
"The Xerox board of directors and management are confident with the strategic direction in which the company is heading, and we will continue to take action to achieve our common goal of creating value for all Xerox shareholders," Xerox said in a statement.
In morning trading, shares of the Norwalk, Connecticut-based company added 62 cents to $32.42. The stock is up about 17 percent in the past year.