Bertha Mkhize was born in 1889 in Embo, near Mkhomazi. Her father, an ox wagon driver died when Bertha was about four years old, after his death her family moved to Inanda. She was one of the first students to attend the Inanda Seminary and thereafter went to Ohlange Institute. Bertha was a teacher until she was about thirty years old, trained as a tailoress and then started a tailoring business in Durban with her brother, also a tailor. She stayed in business until 1965 when the Durban City Council forced African businesses to move out of the area.
Bertha was a member of the Industrial Workers’ Union (ICU) and took part in campaigns against passes for women in 1931 and 1936. She was also active in the African National Congress Women's League and participated in the 1952 Defiance campaign in Durban. Bertha attended the founding conference of the Federation of South African Women (FEDSAW) in early 1954 and was chosen one of the organisation's four national vice-presidents. She was arrested, charged with treason in December 1956 she was the president of the ANC Women’s League. She was one of the defendants in the Treason Trial until she was discharged in December 1957.