From the US, he went to the University of Zambia, Lusaka, where he lectured as a Professor of Physiology. He was there till he returned to Nigeria in 1975. While teaching in the University of Nigeria Enugu campus, from 1975 till 1989, he held many administrative positions, including Head of department, and Dean of Faculty. 'Prof' as many called him did not rest on his laurels, while preoccupied with the teaching job. He conducted research, and wrote a thesis, submitted to the University of London. He subsequently completed the academic cycle when he became a Doctor of Medicine from the University of London in 1977. In 1978, Professor Gabriel Ezeilo became a fellow of the Royal College of Physicians, Edinburgh (FRCP). His next job was to help set up the teaching hospital at the Nnamdi Azikiwe University Nnewi. He was appointed the first Provost of the Nnamdi Azikiwe Teaching Hospital Nnewi from 1989 - 1991. He returned to the University of Nigeria Enugu Campus, where he worked from 1991 - 1994. in 1994, Prof. Ezeilo went to the other side of the planet, to the University of Papua New Guinea, where he worked till 2002, when he came to the University of Malawi. In 2004, He came back to Nigeria, to work as a contract staff of the Ebonyi State University, Abakaliki.