"Diary of a Combatant" covers the period from 1956 until late 1958, days before the Cuban Revolution swept Castro to power.
It begins with his arrival in Cuba aboard the yacht "Granma" with Fidel and Raul Castro and covers his march from the eastern side of the island to the capital.
It was launched in Havana on Tuesday -- which would have been Guevara's 83rd birthday. Guevara's widow Aleida March and one of his daughters were on hand to sign copies.
March told reporters the purpose of publishing the diary is "to acknowledge his thoughts, life and work."
Guevara was killed in Bolivia in 1967.