Martha Koome was born in Kithiu village, Meru County, Kenya in 1960. Her parents were peasant farmers. She received her LLB from the University of Nairobi, Kenya, and attended the Kenya School of Law in 1987, where she graduated with distinction and was then called to the bar. She received her LL.M in Public International Law from the University of London in 2010.

Koome’s career began at Mathenge and Muchemi Advocates as a legal associate. She soon opened a law firm that became one of Kenya’s most successful women's law firms. As an astute lawyer, she represented and defended persons charged with politically instigated offenses during the one-party rule of President Daniel Arap Moi in Kenya.

Koome was appointed as a Commissioner to the African Committee on the Rights and Welfare of Children by the African Union Heads of States in 1995. Additionally, she served as Chairperson of the National Council on the Administration of Justice special task force on children matters and led discussions on the review of the Children’s Act.

In 2003, President Mwai Kibaki appointed Koome as a judge of the High Court, where she headed the family, environmental, and land division for eight years. During her active years as a High Court Judge, she also sat in satellite courts to clear a backlog of cases. Her excellence and hard work earned her an appointment as a Court of Appeal judge in 2012, the same year she was elected as the Chairperson of the Kenya Magistrates and Judges Association.

On April 14, 2021, Koome was shortlisted and interviewed publicly for the position of Chief Justice. She demonstrated a deep understanding of legal and social issues and proved to be a formidable candidate for the role. After being presented with her name, the President referred her to the Kenyan Parliament for vetting and approval. On May 19, 2021, the Parliament approved of her appointment and President Uhuru Kenyatta appointed her Chief Justice, making her the first woman to become a Chief Justice in Kenya.