She also won the 1994 Commonwealth Games 100 metres title.
Onyali-Omagbemi performed especially well in the All-Africa Games, winning a total of 7 individual medals in the short sprints.
She won 100 m in 1991, 1995 and 2003 and took a bronze medal in 1987.
Gold medals in 200 m were taken in 1987, 1995 and 2003.
Furthermore, the Nigerian 4 × 100 m relay team won all races between 1987 and 2003, at the African Games.
Born Mary Onyali, by the time of the 2000 Olympics she was known as Mary Onyali-Omagbemi, having married fellow Nigerian sprinter Victor Omagbemi.
Her consecutive Olympic appearances from 1988 to 2004 made her the first Nigerian to compete at five Olympics.
This feat was equalled by table tennis players Bose Kaffo and Segun Toriola four years later in Beijing, PR China.
Mary Onyali-Omagbemi currently serves as the Special Adviser (Technical) to the Director General of the National Sports Commission in Nigeria, and is a part of the consultation committee for the proposed Sports University of Nigeria, Idumuje-Ugboko.