 Onoja was born in Idah, Kogi State, Nigeria, to Job Idoko Onoja and Mary Omada Onoja.Onoja graduated from Ofante High School in 1985 and then went to the School of Basic Studies in Makurdi where he obtained an Advanced Level Certificate in 1987.He studied at University of Jos from 1987 to 1990 where he earned his Bachelor of Laws LLB, attended Nigerian Law School for his Barrister at Laws to practice law in Nigeria, and did his compulsory National Youth Service Corps at Nkwere Local Government Council in the old Imo State of Nigeria between 1991 and 1992.