More than 2.5 million of the country’s six million citizens are expected to cast their vote for a new president, parliament and local councils.
Incumbent President Ernest Bai Koroma, faces eight candidates, including ex-military leader Julius Maada Bio.
The election will be closely monitored by several thousand local observers.
The results have to be declared within 10 days of voting taking place.
The three main parties in the running are Mr Koroma’s All People’s Congress (APC), Mr Bio’s Sierra Leone People’s Party (SLPP) and the People’s Movement for Democratic Change (PMDC).
The leader of the PMDC, Charles Francis Margai, is the son of Sierra Leone‘s second Prime Minister Albert Margai.
The political manifestation of the rebel Revolutionary United Front (RUF) is also contesting the polls.
The RUF were accused of committing atrocities and employing child soldiers during the civil war.
The west African nation has come a long way since its devastating war in the 1990s, the BBC’s Mark Doyle reports from the capital, Freetown.
Its economy is growing fast – albeit from a very low base – and the elections are set to be held in a peaceful, democratic way, our correspondent says.
But despite significant advances, Sierra Leone remains one of the world’s poorest nations.
A large number of the country’s approximately six million people live on less than $1.25 (80p) a day.