Prosecutors at The Hague said in a statement on Monday that their inquiries would be "impartial and independent, focussing on the individuals who bear the greatest criminal responsibility".
The court has been analysing the situation in Darfur since the United Nations referred to it allegations of rape, murder and plunder in April, following a UN Security Council vote.
Dozens of court officials have begun preparing the investigation, the largest and most important to be handled by the court since it was established in July 2002.
"The investigation will require sustained cooperation from national and international authorities. It will form part of a collective effort, complementing African Union and other initiatives to end the violence in Darfur and to promote justice," Chief Prosecutor Luis Moreno-Ocampo said.
Moreno-Ocampo will brief the UN in New York about his plans to investigate Darfur later in June.
An estimated two million people
have been displaced in Darfur
Sudan has indicated it will not cooperate with the Hague-based court, saying it intends to set up its own tribunal to prosecute crimes.
The vast western Sudanese region of Darfur is the scene of one of the world's worst humanitarian crises.
An estimated 180,000 people have died - many from hunger and disease - and about two million others have been displaced since the conflict began in February 2003.
Darfur's crisis erupted when rebels took up arms against what they saw as years of state neglect and discrimination against that region.
The government is accused of responding with a counter-insurgency campaign in which the Janjawid militia allegedly committed widescale abuses.
"The prosecutor's decision to investigate mass murder and rape in Darfur will start the wheels of justice turning for victims there. As a UN member-state, Khartoum is obligated to cooperate with the ICC," Human Rights Watch spokesman Richard Dicker said in a statement.
"As a UN member-state, Khartoum is obligated to cooperate with the ICC"
Human Rights Watch spokesman
Investigators have said they hope to move quickly and complete their work over a period of months, rather than years.
Once they have gathered evidence and interviewed witnesses, court officials will then consider issuing indictments against individual suspects and seek their extradition to The Hague.
A special UN commission of inquiry on Darfur, which spent several months gathering evidence of war crimes, handed the court its findings, including a list of 51 potential suspects.
The list has not been made public, but suspects could include Sudanese government leaders, rebels and militiamen allegedly acting with government approval against civilian tribes.