The Palestinians formally delivered the UN papers ratifying the Rome Statute -- the legal document establishing the basis of the Hague-based court -- last Friday, the last phase in their accession bid.
"The statute will enter into force for the State of Palestine on April 1, 2015," Ban said in a notification published Tuesday night on the UN's online treaty collection portal.
The secretary-general said he was acting as "depositary" during the ratification process.
The International Criminal Court at The Hague was established in 1998 as a court of last resort to prosecute the most heinous offenses such as war crimes and crimes against humanity in cases where national courts fail.
The Palestinian Authority President Mahmoud Abbas signed the treaty last Wednesday along with 16 international agreements following the UN Security Council's rejection of a draft resolution calling for an end to Israeli occupation of Palestinian territories within three years.
In retaliation, Israeli government blocked the transfer of approximately $125 million in tax revenues collected on behalf of the Palestinian Authority, a move opposed by Washington.
Joining the world's permanent war crimes tribunal means Palestinians could refer specific Israeli actions to the prosecutor and request that they be investigated.
Palestinian sources said their focus would be the illegal Israeli settlement-building in the occupied West Bank and a military offensive last summer that killed more than 2,160 Palestinians in the blockaded Gaza Strip.