It is named for the concelho of Mértola in south-eastern Alentejo, bordering with Spain.

[4] The Mertolenga originated as a colour variant within the Alentejana cattle of Alentejo in south-eastern Portugal, identified in 1873.

The Mertolenga was originally used principally for draught work in the rice fields of Alentejo.

It was also used to assist in moving and handling fighting cattle, in the same way that the Berrenda en Colorado is used in Spain.

[3]: 242  In the twenty-first century it is reared for beef, some of which is marketed as Carne Mertolenga, which has Denominação de Origem Protegida status.