Its name is of Roman origin (Cornelianus) and the city's architectural characteristics possess Visigoth traits.

The first written reference to the city dates from 980 AD, at which time a church and a defense tower to ward off the Saracens already existed in the same place as the current castle (constructed in the fourteenth century).

The city was incorporated into Barcelona's territory in the thirteenth century and, for a short time, belonged to the "Franqueses del Llobregat" in which agricultural activity was principally developed.

Cornellà de Llobregat was subject of a controversy in November 2017 as a result of an opinion piece published in Catalan newspaper El Nacional, in which the inhabitants of Cornellà were accused of being "settlers" by virtue of their immigrant (Xarnego) origin and alleged refusal to integrate or learn the Catalan language.

The article claimed that the working-class "red-circle" of Barcelona, of which Cornellà de Llobregat is an example, is a bastion of Spanish nationalism where "Catalans" are stigmatized.