Until November 2018, Don was the Chief Administrative Officer and Head of Operations and Technology of Citigroup and a member of Citi's Operating Committee. He also held the Executive Chair of the Chief Information Officer Council, which sets global standards for all technology throughout Citi, and led the Digital Governance Office, which drives digital transformation across Citi's businesses. He has played an important role in transforming Citigroup’s Operations and Technology from a loose federation of independent and dispersed entities into a lean, globally-integrated enterprise.

In addition to his technology responsibilities, he was also responsible for: overseeing Citi's Shared Services organization, comprising an integrated global managed services model executed through 34 Citi Service Centers; overseeing Citi's enterprise analytics platform, which transforms raw data into actionable knowledge, creating new insights and value for clients; and managing Citi's global real estate portfolio, generating increased productivity by consolidating Citi's footprint and optimizing the workplace environment.

Prior to joining Citi in 2007, he held the position of Director of Strategy for IBM Japan. In Morgan Stanley, he initially served in numerous roles in strategy, business development, and client technology in the Equities Division and finally became the Head of Business Management for the Institutional Securities Group. He was also a part of Credit Suisse, where he developed and implemented client-centric technology strategies that drove productivity, enhanced client service and improved profitability.

Don is actively involved in several community organizations. He is Co – Chairman of the board of Sheltered harbor, a subsidiary of the Financial Services Information Sharing and Analysis Center (FS-ISAC), Chairman of the Board of Trustees at Manhattanville College and also serves on the board of the American Red Cross in Greater New York, the New York Hall of Science. He is a member of the Gaelic-American Club in Fairfield, CT, Business Committee of Metropolitan Museum of Art and is a Fellow at the Foreign Policy Association. 

A fourth-generation Irish American with ancestral links to County Cork, Ireland on both sides of his family, Don lives in Fairfield CT with his wife, Lisa. They have four sons.