[6][7] Souza joined the Communist Party of India soon after, and co-founded the Bombay Progressive Artists' Group in 1947.

[8] In 1948, Souza's paintings were shown in London's Burlington House as part of an exhibition on Indian Art.

His success as an artist took off following the publication in 1955 of his autobiographical essay Nirvana of a Maggot in Stephen Spender's Encounter magazine.

[12] Souza's career developed steadily, and he participated in several shows, receiving positive reviews from John Berger.

According to Berger, Souza's style "was deliberately eclectic: essentially Expressionist in character", but "also drawing on the post-war Art Brut movement and elements of British Neo-romanticism".

[14] His painting Birth (1955) depicting his mistress Liselotte posing naked while pregnant with their first daughter Keren,[7] set a world auction record in 2008 for the most expensive "Indian" painting sold till then when it was purchased by Tina Ambani for US$2.5 million (Rs 11.3 crore) at a Christie's auction.

[10] In 1954 Souza met Liselotte Kristian (also surnamed Kohn, 1919–1990), a married Jewish actress and Progressive League member, who became his mistress.

[24] Souza's eldest daughter by his partner Liselotte Kristian is the British-Israeli painter Karen (Keren) Souza-Kohn.

[13][18][25] Karen's son is the British-Israeli street artist Solomon Souza, known best for his murals in the Mahane Yehuda Market.