Nicastro grew beneath a Norman castle later held by Frederick II, and was for centuries the principal town of this isthmus — a bishop's seat and, under the Bourbons, the head of a district of Calabria Ulteriore Seconda , alongside Catanzaro, Monteleone and Cotrone.

Sambiase , on the slope above the plain, was a separate agricultural comune with its own thermal springs — the terme that gave the merged city its name.

Sant'Eufemia Lamezia lay on the coastal plain, which for centuries was malarial and largely empty. The reclamation of the plain of Sant'Eufemia , carried out between the late 1920s and the 1930s, transformed it into farmland and then into the infrastructure corridor it is now — airport, motorway junction and the main railway station of Calabria.

The merger was a deliberate act of modern planning. Promoted by senator Arturo Perugini , the enabling law passed in December 1967 and the three comuni were united on 4 January 1968 under the name Lamezia Terme , with the seat at Nicastro. Perugini became the city's first elected mayor in 1970.

Separate football clubs, separate cemeteries and separate patronal feasts survive from the three towns — the merger, as locals often say, happened on paper faster than on the ground.