Economic and regulatory policies are not enough, he wrote, adding: "It is a leader's role, in business or government, to bring people together, not tear them apart."
Dimon's statement comes after the Strategic and Policy Forum, which advised Trump, agreed to disband following the president's inflammatory remarks Tuesday. Dimon was a member of the panel.
Shortly after that decision, Trump tweeted he would be disbanding his two major business councils.
Later Wednesday Mary Barra, General Motors CEO, who was a member of the forum, joined a growing chorus of business leaders in rejecting racial bigotry and calling for the country to come together in the wake of Trump's statements.
"Recent events ... require that we come together as a country and reinforce values and ideals that unite us — tolerance, inclusion and diversity — and speak against those which divide us — racism, bigotry and any politics based on ethnicity," her statement read.
IBM CEO Ginni Rometty, who was a member of the forum, also added her statement to the mix on Wednesday afternoon, noting in a memo CNBC obtained that IBM has worked with every president since Woodrow Wilson and saying the company has always believed "dialogue is critical to progress" but that "this group can no longer serve the purpose for which it was formed."
Earlier, executives from three more major companies quit the president's manufacturing council Wednesday shortly after the Trump tweet.
Jeff Immelt, chairman of GE, Alex Gorsky, CEO of Johnson & Johnson, and the CEO of United Technologies, Gregory Hayes, cited Trump's recent statements regarding the violence in Charlottesville over the weekend as their reasoning.
Immelt said in a statement that he notified council members of his decision Wednesday morning, before Trump's tweet.
"The Committee I joined had the intention to foster policies that promote American manufacturing and growth," Immelt said. "However, given the ongoing tone of the discussion, I no longer feel that this Council can accomplish these goals."
Those three became the ninth, 10th and 11th resignations from the manufacturing council as pressure mounted on the executives in the wake of Trump's waffling responses.
The exodus began with Merck CEO Kenneth Frazier on Monday, who said, "As CEO of Merck and as a matter of personal conscience, I feel a responsibility to take a stand against intolerance and extremism."
By that evening, two more executives joined Frazier in resigning, Keven Plank of Under Armour and Intel's Brian Krzanich.
After Trump's Tuesday news conference walking back his Monday condemnation of neo-Nazis and KKK members marching in Charlottesville, the executives again found themselves backed into a corner.
After that, the floodgates opened.
Correction: Jeff Immelt is chairman of GE. An earlier version misstated his title.