"The prognosis from my doctors is excellent," Dimon, 58, said in an email to investors and employees on Tuesday.
"The cancer was caught quickly, and my condition is curable," he said.
Dimon, who has served as chief executive and chairman of the company since 2006, said the cancer is "confined" to its original site and to lymph nodes on the right side of his neck. He will begin eight weeks of radiation and chemotherapy treatment.
He added that he feels "very good now," and has no plans for a leave of absence.