Saturday's deal comes after negotiations between the Khartoum government and a coalition of rebel groups known as the Eastern Front.
Omar al-Bashir, Sudan's president, called the peace deal an example of "Africans solving an African problem without foreign help".
He reiterated that Sudan rejected a UN proposal to send a peacekeeping force to Darfur.
Mussa Mohammed Ahmed, chief of the Eastern Front, called the accord historic, saying it "definitively turns the page on conflict and opens the way to development".
Mustafa Osman Ismail, chief government negotiator, said earlier on Saturday that the final protocol on power-sharing had been agreed upon following earlier deals on the issues of wealth-sharing and security.
The signing ceremony, held in the presidential palace gardens, was followed by an evening meal to break a day of fasting during Ramadan.
Third peace deal
The deal is the third peace agreement signed by Khartoum with rebel groups in various parts of the largest nation in Africa in less than two years.
An agreement between Khartoum and the main rebel faction in the Western region of Darfur was signed in May this year but has failed to take hold.
A peace deal was also signed between Khartoum and southern rebels in January 2005, bringing an end to more than two decades of fighting, the longest civil war in Africa.
The former rebel Sudan People's Liberation Movement is now in a national unity government with al-Bashir's National Congress, but relations have often been strained.
Aljazeera says that Andrew Natsios, George W Bush's, the US president, special envoy for Sudan, has begun talks with Sudanese officials on Security Council resolution 1706 on Darfur.
The resolution "invites the consent of the [Sudanese] government" for the deployment of UN troops in the region.
Natsios, who arrived in Khartoum last night, met today with Lam Akol, the foreign minister and Minni Arcua Minnawi, senior assistant to the president and chairman of the regional interim authority of Darfur.
The talks focused on the humanitarian situation in Darfur and prospects for a breakthrough to achieve peace and security in the region.