Returning to Portugal, Possoz divided her time between the Lapa part of Lisbon, almost always in the company of her sister Jeanne and her friend Alice Rey Colaço, and the family home in Estoril. Her father died in 1912. After the overthrow of the monarchy and rebelling against the conservatism of Portuguese society and its conventional approach to art, she joined the emerging modernist movement in Portugal. She started to exhibit at the "Sociedade Nacional de Belas Artes" (Society of Fine Arts) in 1909 and rapidly became known, being a regular exhibitor at the Society's annual salons until 1916. She would also exhibit at the Humourist and Modernist Exhibitions from 1913 to 1926, along with José de Almada Negreiros and others. She was one of the few female artists of her generation to organize individual exhibitions of her work, in oil painting, pencil drawing, gouache or watercolour. Invited to participate she was the only female exhibiting in the 2nd Exhibition of Humourists, in 1913, and in the Exhibition of the "Five Independents" in 1923. In a male-dominated society, Possoz was regarded as an equal by her fellow artists.