Legislature chief Diosdado Cabello made the announcement on national television.
He said Maduro would be sworn in at 7 p.m. in the same military academy complex where the president has been lying in state.
On Tuesday, after announcing Chavez's death, the government said Maduro would both be acting president and the presidential candidate of the governing party.
The opposition cried foul. Venezuela's constitution specifies that upon Chavez's death, Cabello should have become interim president and elections for a new president called within 30 days.
A former Supreme Court judge, Blanca Rosa Marmo, said that Maduro could not run for president as vice president. She said the government is not adhering to the constitution. She said it's Cabello, not Maduro, who should be sworn in.
The government said Tuesday that the election would be convoked in 30 days. It is not clear when they will be held.
Cabello said Maduro would be sworn in and call the elections.