A resolution adopted on Monday by all 193 nations in the UN General Assembly calls on any nations with information about the air crash in which Hammarskjöld died to disclose it.
The resolution cites new and previously ignored evidence and establishes an independent panel of experts to examine the new information.
The inquiry hopes to resolve the mystery surrounding the death of the renowned Swedish diplomat. Hammarskjöld and his staff were travelling in a jet over what is now Zambia but was then the British colony of Northern Rhodesia when the plane crashed in a forest.
At the time, both Sweden and Northern Rhodesia blamed the pilot. A 1962 investigation failed to come to any conclusion about the cause of the crash, but evidence presented in a 2011 book suggests that the plane was shot down by mercenaries, the Wall Street Journal reports.