Nora, as she was known, was the daughter of the civil engineer Horace Darwin and his wife Emma Farrer, daughter of Thomas Farrer, 1st Baron Farrer. She married Alan Barlow, son of the Royal Physician Sir Thomas Barlow. They had six children:

• Joan Helen Barlow (26 May 1912 — 21 February 1954)
• Sir Thomas Erasmus Barlow, 3rd Bt. (23 January 1914 — 12 October 2003), naval officer.
• Erasmus Darwin Barlow (15 April 1915 — 2 August 2005)
• Andrew Dalmahoy Barlow (b. 16 September 1916)
• Hilda Horatia Barlow (b. 14 September 1919) married psychoanalyst John Hunter Padel; their daughter is the poet Ruth Padel.
• Horace Basil Barlow (b. 8 December 1921)

She published an unexpurgated version of The Autobiography of Charles Darwin, which had previously had personal and religious material removed by his son, Francis. She also edited several collections of letters and notes, including correspondence between Darwin and John Stevens Henslow, his mentor.

The Columbine flower cultivar Aquilegia "Nora Barlow" is named after Barlow.

Nora Barlow appears as a supporting character in Scott Westerfelds's 2009 young-adult steampunk novel Leviathan. In Westerfeld's alternate history, Barlow is a prominent genetic engineer.