The president will be chosen "without debate" by lawmakers "for a single six-year term," and not by the public, according to the new text.
The vote comes less than a month before the next legislative elections in Togo, but it is not yet known when the change — which was approved with 89 votes in favor, one against and one abstention — will come into force.
Currently, the president can serve a maximum of two five-year terms.
The change to the constitution, proposed by a group of lawmakers mostly from the Union for the Republic (UNIR) ruling party, was adopted almost unanimously.
The country's opposition, which boycotted the last legislative elections in 2018 and denounced "irregularities" in the electoral census, is poorly represented in the national assembly.
The new constitution also introduces the position of "president of the council of ministers" with "full authority and power to manage the affairs of the government and to be held accountable accordingly."
The president of the council of ministers is "the leader of the party or the leader of the majority coalition of parties following the legislative elections. The position will be held for a six-year term," according to the text.
"The head of state is practically divested of his powers in favor of the president of the council of ministers, who becomes the person who represents the Togolese Republic abroad, and who effectively leads the country in its day-to-day management," said Tchitchao Tchalim, chairman of the national assembly's committee on constitutional laws, legislation and general administration.
The new text will mark Togo's entry into its fifth republic, with the last major constitutional change dating back to 1992.
It comes less than a month before the next legislative elections, due to be held on April 20 at the same time as regional elections, in which the opposition has announced its participation.
In 2019, members of parliament revised the constitution to limit presidential terms to two, but it did not apply retrospectively, leaving President Faure Gnassingbe free to stand for the next two elections.
Gnassingbe — in power since 2005 — succeeded his father General Gnassingbe Eyadema, who seized power in a coup more than 50 years ago.