Mordecai has been a partner in Harare law firm Gill, Godlonton & Gerrans for the past 21 years. He was admitted as an attorney of the High Court in 1978, after completing his law degree at the then University of Rhodesia in 1975. He was a partner in the Bulawayo law firm Lazarus & Sarif before joining Gill, Godlonton & Gerrans. He is a member of the Law Society of Zimbabwe and the International Bar Association. He sits on the boards of a number of companies in Zimbabwe, including those of Old Mutual, Truworths and RioZim. He is a former member of the board of the Reserve Bank of Zimbabwe. He also sits on the boards of several private educational institutions in Harare and Bulawayo, as well as on the board of Zimbabwe Lawyers for Human Rights. He is a past president of the Harare Dawn Rotary Club
His areas of specialisation include corporate and commercial law, labour and commercial litigation, and arbitration in labour and commercial disputes.