The PRT was founded in 1965 by Mario Roberto Santucho (FRIP) and Leandro Fote by merging two existing far-left political parties.

The FRIP had been founded by Francisco René Santucho and his brother Mario Roberto in 1961 at Santiago del Estero, Argentina.

It was a ruralist, indigenist (pro-Amerindian) and revolutionary movement that extended its influence throughout the provinces of Tucumán, Chaco and Salta.

Palabra Obrera, on the other hand was a Trotskyist party founded by Nahuel Moreno, active in the trade unions.

That same year a related organisation was founded in Argentina, the ERP (People's Revolutionary Army) that became the strongest rural guerrilla movement in South America during the 1970s.