Joseph P. Mullinix earned an AB in economics from Georgetown in 1964 and an MBA from Chicago's Graduate School of Business Administration in 1965. From 1969 to 1972 he was in a doctoral program concentrating in management control systems at Harvard's Graduate School of Business Administration. From 1972 to 1981, he worked in the Executive Office of the President of the US. In 1982, he was a senior financial analyst at Goldman Sachs.

Mullinix joined Columbia in 1983 as vice provost for academic planning and resource management, responsible for the management of the revenues and expenditures of the University's academic programs. A year later, he was named Senior Vice President. In his new role, he was directly responsible for residence halls, dining, health services, security, and technology. He oversaw Columbia's planning and budget activities, personnel and facilities operations, campus life, student financial and information services, and other auxiliary and administrative services.

In 1991, still under the same title, he took on new responsibilities as the chief financial officer. He oversaw the treasurer and controller, vice president for investments, director of internal audit, director of institutional real estate, and director of project development.

Mullinix served as the top planner, administrator and resource manager for 10 years at Columbia. In 1993, he left Columbia to assume a similar position at Yale. On his departure his position was split again into two: executive vice president for administration and vice president for finance.