Hon. Justice P. O. Nnadi was born on the 12th of March 1955 at Emekuku to the family of Late Pa Stephen O. Nnadi and Lolo Regina A. Nnadi all of Ndegbelu Awaka in the Owerri North Local Government Area of Imo State of Nigeria.
He had his early education at Our Lady of Mount Carmel Primary School Emekuku (Now Chief Obi Memorial Primary School Emekuku) from where he gained admission to the Prestigeous Holy Ghost College Owerri and passed the WASC Examination in Division I in 1975 and the Higher School Certificate Examination in 4 papers in 1977.
He gained direct entry admission to the Cosmopolitan University of Lagos (Akoka) where he studied Law and obtained the Bachelor of Laws Degree (LLB Hons) in 1981 and was called to the Nigeria Bar in 1982.
Hon. Justice P. O. Nnadi served in the NYSC Scheme as a Legal Counsel to the Anambra State House of Assembly from 1982 to July 1983 and was in Private Legal Practice at Owerri from 1983 to 1988..  He later joined the Judicial Service of Imo State as a Senior Magistrate and rose to the rank of Chief Magistrate in 1992, Deputy Chief Registrar (High Court) from 1993 to 1995, Chief Registrar (High Court) from 1995 to 1998 and  was elevated to the High Court Bench in April 1998 and has served in that capacity until 18th December 2014 when he was elevated to the position of Chief Judge of Imo State, a position he still holds till date.
As a Judge he served in election tribunals as member and chairman in different states of Nigeria and is a widely travelled man.
As a Chief Judge, he is the chairman of the Judicial Service commission of Imo State, member body of benchers of the legal profession, member board of governors of National Judicial Institute (NJI) and member National Judicial Council (NJC). .
He has attended several professional and administrative conferences, seminars and workshop at both domestic and international Fora including the

Hon. Justice P. O. Nnadi is a proud member of the enviable Catholic Order of the Knights of St Mulumba (4th degree).  He is married to Dr. Mrs. Ine Nnadi Associate Professor of Law, Imo State University Owerri and they have twin boys.
He enjoys studying human behaviour, listening to music and playing table tennis and Basket Ball.