Petrona Viera was among the first Uruguayan women painters to gain recognition in her country. She was the oldest of 11 children born to Carmen Garino and Feliciano Viera, the president of Uruguay, between 1915 and 1919. At the age of two, she suffered an illness that left her deaf, which impeded her speech acquisition. Since there was no inclusive educational system at that time, she was home schooled by Madeleine de Larnaudie, a French educator who specialised in teaching deaf children, thanks to whom P. Viera could begin to develop the skills that would allow her to communicate with those around her.
When she was about 20, P. Viera began to be home schooled in art by teachers from the Círculo de Bellas Artes [CBA, Fine arts’ circle], a pioneering space for training artists in Uruguay, founded in 1905. From 1920 to 1922, she took classes with the Uruguayan-Catalan painter Vicente Puig (1882–1965), who taught her how to use paintbrushes and work with oils. In 1922, she began to study with Guillermo Laborde (1886–1940), who introduced her to Planism, an artistic movement that arose in Uruguay during the 1920s and was characterised by two-dimensional representations and a vibrant, bright palette. G. Laborde encouraged her to show her work in salons and exhibitions. In 1923, her work first appeared in the Second Spring Salon of the Círculo de Bellas Artes. She regularly took part in local exhibitions as well as international group exhibitions in Buenos Aires, Seville, Paris etc. In 1928 she mounted her first solo show in Montevideo.

During the period when she worked with G. Laborde, P. Viera mainly produced oil paintings, along with occasional tempura and water colour pieces, and pencil drawings. Her main subjects in the 1920s, the decade most representative of her career, were children’s games (many paintings from this period are titled Recreo [Recess]) and scenes from daily life and chores, such as Escribiendo [Writing, 1923] and Juntando Fruta [Gathering Fruit, 1927], as well as portraits (Autorretrato [Self-Portrait, c. 1930], and Retrato de Luis E. Pombo [Portrait of Luis E. Pombo, c. 1930]). This period reflects her life in the country home where she lived with her family. Such broad representation of women and girls, with girls telling each other stories and women writing or working together, was unprecedented in Uruguayan art. Starting in 1930, she began to produce landscapes and female nude studies.

Between 1940 and 1950, P. Viera worked with Guillermo Rodríguez (1889–1959), who taught her engraving. Her line became stronger in her woodcuts as she moved away from Planism. From the 1940s until her death she took up still lifes of flowers, fruit and everyday objects.

Between 1966 and 1968 her mother donated 995 of her works to the Museo Nacional de Artes Visuales. Even so, it was not until 2020 that the museum held the first – and highly anticipated – retrospective of her work.