It is still unclear whether President Omar al-Bashir, who is wanted by the International Criminal Court for alleged war crimes in war-torn Darfur, will stand for re-election.
The elections for president, national and state legislators and for governors will be only the second since Bashir seized power 25 years ago in an Islamist-backed coup.
Elections which Bashir won in 2010 were marred by opposition boycotts, with monitors saying the process failed to meet international standards.
“We are announcing the timetable for 2015 elections because it is a constitutional and legal commitment,” Mukhtar al-Assam, chief of the National Election Commission, told reporters.
He said the vote will take place on April 2.
Candidate nominations are to open on December 31, followed by campaigning from February 13 to March 30.
Assam’s announcement came a day after a leading opposition party, Reform Now, and several small parties said they were “not committed” to the polls.
Any vote must form part of a national political dialogue which Bashir announced in January to discuss multiple crises in the impoverished, war-ravaged nation, they said.
After preliminary talks with Bashir, Reform Now and the other parties say the discussions can only continue if the proposed elections are covered.
The group also wants a two-year “transitional administration” to implement the outcome of the dialogue.
The government has hinted at greater political liberties as part of a reaching out to other political parties.
But the arrest of political figures and continued press censorship have raised doubts over Bashir’s commitment to change.