Khayelihle Kenneth Mthiyane was born in Ndwedwe, KwaZulu-Natal, on 13 September 1944. He attended school in Durban and matriculated by private study. He is married to S'Thandiwe Phyllis Mthiyane (born Khuzwayo), with whom he has four daughters.
Mthiyane obtained the B.Iuris degree from UNISA in 1972. He obtained an LL.B in 1984 and an LL.M in 1994, both from the University of Natal, Durban.
Mthiyane was admitted as an attorney in 1975 and later established K. K. Mthiyane and Company, a law firm in Durban dealing mainly with public interest and political cases, apart from general commercial, civil and criminal cases involving litigants from the then disadvantaged communities.
Mthiyane joined the Durban Bar in 1984 and took silk in 1995.
During 1995, he chaired two Commissions of Enquiry which investigated racism at the University of Zululand and the then University of Durban Westville.
In the last term of 1995, Mthiyane served as an Acting Judge in the Ciskei Division of the Supreme Court at Bhisho.
In 1997, he headed the three-person Mthiyane Commission which investigated corruption, racism and other irregularities in twenty-two provincial hospitals in KwaZulu-Natal with a view to establishing clean governance. The report and the recommendations of the Commission resulted in the abatement chaos that had threatened to destabilise service delivery in the province and a number of dismissals and prosecutions followed.
In 1997, Mthiyane was appointed as a Judge of the Natal Supreme Court, and in 2000, he served as an Acting Judge of the Supreme Court of Appeal.
In 2001, Mthiyane was appointed as a Judge of the Supreme Court of Appeal.
In 2002, he was appointed as the Chairperson and Head of the Electoral Court.
Since 2006, Mthiyane has served as the Vice-Chairperson of the Rules Board for Courts of Law in South Africa.
During May 2008, Mthiyane served as an Acting Judge in the Supreme Court of Namibia.
In 2011, Mthiyane was appointed as an Acting Judge of the Constitutional Court of South Africa.
- Mthiyane has served as the chairperson of the Durban branch of the National Association of Democratic Lawyers.
- He has also served as an instructor and part-time lecturer at the Practical Training School for attorneys at Howard College, University of Natal, run by the Association of Law Societies, where he taught supreme court practice and procedure.
- Leading up to the first democratic elections in South Africa in 1994, Mthiyane actively participated in providing legal assistance and voter education to the (until then) disenfranchised communities.
- Member of the Council of the University of Pretoria, as donor representative, for seventeen years, and was and still is, an assessor member of the Faculty of Law of the University of Pretoria.
- He serves as a Council Member of The Beatrice St Congregational Church in Durban.
- Mthiyane is involved in sport and in various other community activities, and he enjoys reading, gym and golf.