Fayemi recently resigned as Buhari's minister to seek a second term as Ekiti State governor.
Dr Fayemi is the APC's candidate for Ekiti's July 14 gubernatorial election as he seeks a second term to lead the state.
President Buhari's Personal Assistant on New Media, Bashir Ahmad, confirmed on his Twitter account (@BashirAhmaad) that the president will be at the rally.
He posted, "President Muhammadu Buhari will visit Ekiti State today to attend the All Progressives Congress (APC) Mega Rally at the Oluyemi Kayode Stadium in Ado Ekiti, ahead of the State's Gubernatorial Election."
Fayemi was Ekiti State governor between 2010 and 2014 before he was defeated by Ayodele Fayose during his re-election attempt.
The July 14 election is expected to be a straight battle between Fayemi and and Fayose's deputy, Prof. Kolapo Olusola of the PDP.