The Turkish ambassador to the Council of Europe made the pledge on Friday by signing protocol number 13 of the European Convention on Human Rights.
The protocol obliges countries to abolish the death penalty in all circumstances, including times of conflict.
Turkey had already signed a protocol concerning the abolition of capital punishment in peace time following a vote in the Turkish parliament in August 2002.
A moratorium on the death penalty has been in place in Turkey since 1984.
Human rights reforms
The move is part of a human rights reform programme which the EU considers vital if negotiations over Ankara's adhesion to the alliance are to get underway.
Under EU criteria countries are required to abolish capital punishment for any crime.
Western human rights groups are sure to welcome the move, with many of them campaigning for an end to the death penalty for years.
"The death penalty is the ulitimate cruel, inhuman and degrading punishment. It violates the right to life. It is irrevocable and can be inflicted on the innocent. It has never been shown to deter crime more effectively than other punishment"
Amnesty International was not available to comment on Turkey's decision, but describes the death penalty as "the ulitimate cruel, inhuman and degrading punishment.
"It violates the right to life. It is irrevocable and can be inflicted on the innocent. It has never been shown to deter crime more effectively than other punishemnt".
However, Massoud Shadjareh, of the London-based Islamic Human Rights Commission, gave a more guarded welcome to the move.
He said although all humans deserve to be treated equally, different cultures have different interpretations on what "human rights" means.
The West's human rights rhetoric is full of hypocrisy and double-standards and is often used as a political tool to oppress the world's weaker nations, he added.
"We welcome this development because at the moment what you have in Turkey is not a just system," Shadjareh said.
"This is a place where the head of the judiciary openly boasts about torture, and people are imprisoned for organising demonstrations against Israel. So anything that helps this injustice to stop is a postive step."
But he added: "In the context of a just Islamic society the death penalty has an important role to play, but I feel that at the moment in Turkey it is too open to abuse."
And Shadjareh was ambivalent about Turkey's desire to enter the EU in the first place.
"In the context of a just Islamic society the death penalty has an important role to play, but I feel that at the moment in Turkey it is too open to abuse"
Islamic Human Rights Commission
"If joining the EU will help Turkey to improve its human rights record then that is good thing, but it strikes me as peculiar that Turkey would want to be part of a club that doesn't want it to join.
"If you look at the statements coming out of France and Germany in particular, it is clear that they see the EU as one big Judeo-Christian club."
The EU is to decide in December 2004 if Turkey, a secular but mainly Muslim country, has made enough progress in democratic reforms to open membership talks.
European Commission head Romano Prodi is to visit Turkey next week, the first such visit by an EU executive since Turkey signed an association agreement in 1993.