The Economic Community of West African States said its mission would "interact with the main stakeholders on the latest developments" in Togo before legislative and regional elections on April 29.
The delegation is led by Maman Sambo Sidikou, a former head of the African Union's mission in Mali and the Sahel, and will stay from Monday until April 20 following a government invitation, ECOWAS added.
Tensions have soared in Togo since last month, when lawmakers backed a constitutional reform that would move the country to a parliamentary system where lawmakers would elect the president for a six-year term.
The opposition fears it is a ploy to extend the rule of Gnassingbe, who has been in office since 2005 and won re-election in multiple votes condemned as fraudulent by his rivals.
Togolese authorities banned planned protests against the reform by the opposition and civil society groups in recent days, further ratcheting up tensions.
Public protests have been outlawed since 2022 after an attack at a market in the capital Lome that left a gendarme dead.
The opposition, which boycotted the last legislative elections in 2018, is now focusing its efforts on the April 29 polls that were pushed back from an initial date of April 20.
The National Assembly is dominated by the UNIR party of Gnassingbe, who came to office in 2005, succeeding his father who had remained in power for nearly 38 years following a coup.