In a joint statement after three days of fence-mending talks in Khartoum, the two sides said they would "immediately" re-establish diplomatic ties and pledged not to interfere in each other's affairs or host rebels fighting the other nation.
More than three years of ethnic unrest in Sudan's western region of Darfur has spilled over into neighbouring Chad, with tens of thousands of refugees crossing the border to escape the fighting.
On Sunday, Ahmat Allami, the Chadian foreign minister, and his Sudanese counterpart, Lam Akol Ajawin, announced the creation of a joint military-security commission and a joint force to secure their border.
Resumed bilateral cooperation was also planned in all areas "of common interest", the statement said.
Allami said Chad would "remain committed" to the accords and expressed hope that the restoration of relations would help ease the situation in Darfur.
The combined effect of war and famine there has left as many as 300,000 people dead in the region and displaced more than two million.
On April 14, the Chadian president, Idriss Deby Itno had announced the breaking of relations after rebels from the United Front for Change (FUC) launched an abortive assault on N'Djamena with alleged Sudanese support.
That rupture came despite a summit in Libya in February which had already tried to mend ties between the two governments after N'Djamena pronounced itself in a "state of belligerence" with Khartoum in December owing to its alleged support for the rebels.