The incumbent, 53, has led the country of eight million people since 2005 following the death of his father Gnassingbe Eyadema, who ruled with an iron fist for 38 years.
The head of state travelled to the north of the country to vote in Kara, the Gnassingbe's hometown.
The incumbent faces opposition from six other candidates who face a mammoth task to persuade the 3.6 million registered voters to oust him.
The ballot boxes opened at 07:00 am local time and voters flocked to the country's 9,376 voting bureaus.
RFI correspondent Peter Dogbe, quotes Hery Rajaonarimampianina, head of the African Union observer mission to the Togo elections, as saying that his team did not witness any disturbances in any of the five regions of the country.
Main opposition leader Jean-Pierre Fabre of the National Alliance for Change came second at the last two elections but has failed to keep the opposition united.
Prevent fraud
He called on the people to vote in numbers "to prevent fraud and allow for a second round".
Agbeyome Kodjo, who served as prime minister under Gnassingbe's father, is seen as a potential dark horse after winning the backing of an influential Catholic archbishop.
"The Togolese want change, they want an alternative," said Kodjo.
"And when we see all this mobilisation and all the methods of fraud put in place by the government, if at the end of the election, the government dares to say that it has won, imagine the rest."
One name not on the ballot is Tikpi Atchadam, a politician from the second city of Sokode who shot to prominence in 2017 at the head of anti-government protests.
But he fled Togo for Ghana in the face of a crackdown by the authorities on his supporters and has seen his influence dwindle.
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