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.[2] 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,[3] and is a part of the consultation committee for the proposed Sports University of Nigeria, Idumuje-Ugboko.
On the 21st of September 2020, she was made one of the ambassadors of the re-branded National Principal's Cup; a grassroots championship tournament that was popular across Nigeria that discovered many talents, some who were former Super Eagles stars.[4]