She is the daughter of Femi and Feyi Adegoke who are of Nigerian origin. Her father was a GP and her mother is a Professor of physiology. Badenoch's childhood included living in Lagos, Nigeria and in the United States, where her mother lectured.

Kemi is married to Hamish Badenoch and they have two daughters and a son. She describes herself as a cultural Christian and notes that her maternal grandfather was a Methodist minister in Nigeria. Badenoch lost her father Femi in February 2022.

She was one of eight persons who vied for the Office of The UK Prime Minister in 2022.