Professor Olanrewaju Adesola Onadeko attended the University of Ife, Ile-Ife (now Obafemi Awolowo University) and was called to the Nigerian Bar in July 1977. He was subsequently at the London School of Economics and Political Science (LSE), University of London where he obtained the Master of Laws degree (LL.M). He was awarded the honorary degree of Doctor of Laws, (LL.D), by the B.P.P. University, London, United Kingdom in November 2016.
He started his career in the Ogun State Ministry of Justice as a Law Officer (State Counsel). Thereafter, he joined the academic staff of the Nigerian Law School as a Lecturer, and he has held all academic positions.
In 1989, he went on secondment by the Federal Government, to the Republic of the Gambia as Director of Public Prosecutions (DPP). He returned from that assignment in October 1994 to continue his career at the Nigerian Law School.
He was appointed the Secretary to the Council of Legal Education and Director of Administration of the Nigerian Law School from March 2001 to December 2004. In January 2005, he was appointed the Deputy Director-General and Head of the Lagos Campus of the Nigerian Law School. In 2013, he was appointed the 8th Director-General of the Nigerian Law School.
He was the inaugural Chairman of the Editorial Board of the Nigerian Law and Practice Journal. He was also the Editorial Board Chairman of the Publication: Fifty Years of Legal Education in Nigeria – Challenges and Next Steps; to commemorate 50 years of the Council of Legal Education. He is the author of the book: The Nigerian Criminal Trial Procedure. He is a Professor of Law at Ajayi Crowther University, Oyo State.