In 1977 she was is "Kenya’s first woman bank manager of Barclays Bank". "Later she broke the barriers of male dominance in the banking industry, ascending to become the first woman bank manager in Kenya. And there she relentlessly forged the way for the bank to start offering loans to women. She was among founders of the Kenya Women Finance Trust (KWFT) in 1992, becoming their first chairperson."
- "In the field of education, she has pioneered the creation of one of the most successful chain of private schools in East and Central Africa with over 1000 pupils — the Makini Schools, which has topped the Kenya Certificate of Primary Education performance countrywide more than once and twice produced Kenya’s top girl student...
- "She would later organise a tripartite programme between Women’s World Banking (WWB), Barclays Bank and KWFT.
- "Her work with WWB saw her set up affiliates in Gambia, Senegal, Uganda, Zambia and Zimbabwe. She later held the position of senior adviser to the President of the African Development Bank in Abidjan, Cote d’Ivoire.
- "She is also recognised internationally for her service as the Vice President of WWB in New York between 1990 and 1992. She has served on several committees, including the World Bank’s External Gender Consultative Group (EGCG) and women’s credit organisations across Africa. In 1993 she received the International Woman of the Year Award in recognition of her services to finance." 
- Margaret Oganda, "[http://www.eastandard.net/archives/cl/hm_news/news.php?articleid=35022 Mary Okelo: Legend with a cap full of firsts\", The Standard, January 15, 2006.