Members of Aslef on London Tramlink, based in Croydon, will walk out on September 12, following strikes in June and July.
Aslef said the drivers, and other staff whose pay has been frozen for almost two years, have been offered a 3% pay rise, while RPI inflation has soared to more than 12%.
Finn Brennan, Aslef’s full-time organiser on Tramlink, said: “There has been no contact from Tramlink management and no new offer since our last strike in the middle of July.
“It seems FirstGroup, which operates the tram system on behalf of TfL, doesn’t care about either the welfare of their staff or the impact on their passengers of more disruption.
“Their offer means a huge wage cut for staff who face being unable to heat their homes and pay their bills this winter.
“We are having to strike again because management are not prepared to make anything like a fair offer that reflects the real cost of living in this country.
“FirstGroup are prioritising the pay and perks of their bosses above a fair deal for staff.
“Staff on Tramlink are absolutely right to refuse to accept a pay cut so that fat cats can get even fatter.
“We will be calling on local political leaders to join us on the picket line to show support for workers fighting for a fair deal to help them cope with the cost-of-living crisis.”