The pontiff called putting someone in jail for life "a hidden death sentence" in a speech given to delegates from the International Association of Penal Law.
He also severely criticised countries that torture prisoners.
According to The Guardian, Pope Francis told delegates: "All Christians and men of good faith are therefore called upon today to fight, not only for the abolition of the death penalty - whether it is legal or illegal and in all its forms...but also to improve the conditions of incarceration.
"In recent decades a belief has spread that through public punishment the most diverse social problems can be resolved, as if different diseases could all be cured by the same medicine."
Pope Francis also attacked countries that have agreed to US demands to send terror suspects to prisons in parts of the world where torture is allowed or not actively stopped.
"These abuses will only stop if the international community firmly commits to recognising...the principle of placing human dignity above all else," he said.
The pope also hinted that many countries still apply the death penalty even though they have abolished it.
According to Catholic News Service, he said these killings are often said to be "clashes with offenders or presented as the undesired consequences of the reasonable, necessary and proportionate use of force to apply the law".
The pope also slammed the incarceration of prisoners without trial, saying more than one in two inmates in some countries had not had a fair public hearing.