She was the eldest of seven children of Scottish—English parents William McKenzie Angus and Ethel Violet Crabtree.

[1] Angus married Alfred Cook, a fellow artist and brother of James, on 13 June 1930, but they separated in 1934, and divorced in 1939.

[5] In a difficult financial position after her divorce she took on different jobs including teaching and as an illustrator for the Press.

[1] In the early 1940s, Rita Angus had an affair with composer Douglas Lilburn, whom she met in 1941; she became pregnant but miscarried.

[9] From December 1969, Angus' condition rapidly deteriorated; she died in Wellington Hospital of ovarian cancer on 25 January 1970, aged 61.

[6] She was also influenced by the English painter Christopher Perkins' 1931 painting of Mount Taranaki,[11] a response to New Zealand's distinctive clear lighting.

One of the most famous of these is Cass (1936)[12] in which she portrayed the bare emptiness of the Canterbury landscape using simplified forms and mostly unblended colours arranged in sections in a style remiscent of poster art.

[1] Angus also painted 55 self-portraits, particularly during her later years when she became afflicted with increasingly serious bouts of narcissistic disorder.

[19] Four of Angus's paintings were featured on a set of postange stamps issued by New Zealand Post in 1983 to mark the 75th anniversary of the artist's birth.