Born in Agila, Ado local government on November 15, 1972, Onoja is a lawyer.

He started educational pursuits in 1977 at Local Government Education Authority, LGEA School, Apa I, in Ado LGA for the First School Leaving Certificate, FSLC, which he obtained in 1982. Between 1983 and 1988, Onoja attended Government Secondary School, Agila for the General Certificate in Education, GCE, ordinary, level. From 1990 to 1992, he attended Benue State Polytechnic Ugbokolo, and graduated with a diploma in Law. In 1994, he proceeded to the University of Abuja where he graduated in 1998 with an LLB (Hons). He later attended the Nigerian Law Schoo between 2000 and 2001 after which he was called to bar.

Barrister Onoja started his working career with Federal Ministry of Justice as Pupil State Council in the Department of Public Prosecution from 2001 to 2002. The following year, he joined Monsoons Resources Investment Nig. Ltd. as Company Secretary and served until 2009. He became Principal Partner in J.O. Onoja and Partners in 2010, a position he retained until 2011 when he became chairman, caretaker committee, Ado Local Government Council between January 2011 and April 2012. After his brief sojourn in politics, he returned to Monsoons Resources Investment Nig. Ltd. as Company Secretary/ Vice Chairman in 2012, and served until his appointment as Commissioner.