According to newspaper Correio da Manhã, the pint-sized pop star attended last week’s MEO Sudoeste festival in Zambujeira do Mar (Odemira, Alentejo) to watch boyfriend rapper Mac Miller perform.
Beforehand, the newspaper claims, Grande had been in Lisbon to peruse property.
Should this prove true the singer will join other celebrities including Madonna, Michael Fassbender and Monica Belucci to invest in real estate in the Portuguese capital.
Madonna recently purchased a multi-million-euro estate in Sintra, while Fassbender owns a duplex apartment in a luxury development in the heart of the city.
Ariana Grande had already been seen touring around Lisbon in June when she was in the city to perform a concert at the MEO Arena.