Moran began his career with Mutual of America in 1975, and became the first President to be appointed from within the company in 1994. In October 1995, he was appointed Chief Executive Officer and remained in this role for 21 years, before retiring in April 2016. He was appointed Chairman of the Board in June 2005, a position he held until he retired in May 2018. Moran was instrumental in the company's growth to a financially strong mutual life insurance company with over $20 billion in assets.
Moran served in several insurance industry leadership positions, including his service as Chairman of the Life Insurance Council of New York and Chairman of the MIB Group. He was an advisory board member to the "Observatory on Europe 2007", improving European competitiveness and integration. Moran presented at the World Economic Forum in Davos and at the Petra Conference of Nobel Laureates. He also served on the board of directors of the Bank of Ireland and Aer Lingus.
Moran also served on many not-for-profit boards, including the board of the New York Catholic Foundation, the Alfred E. Smith Memorial Foundation, American Cancer Society, the Greater New York Councils of the Boy Scouts, the Viscardi Center, WNET, Manhattan College, the National Committee on American Foreign Policy, the Irish Hunger Memorial, and as chairman of the board of Concern Worldwide. Moran was also the chairman of the North American advisory board of the Michael Smurfit Graduate Business School.
In recognition of his business success and commitment to caring, Moran received numerous awards, including the Calvary Hospital Medal of Honor, the St. Elizabeth Seton Award from the National Catholic Education Association, the Terence Cardinal Cooke Medal, the New York City Fire Department Humanitarian Award, the commissioner's Award by the New York City Police Foundation, the Pierre Toussaint Medallion Honor, and the Ellis Island Medal of Honor. For his support of the international relief organization, Concern Worldwide, Moran was recognized by the prime minister of Ireland, who commented that "his selfless actions have improved the lives of thousands." In 2015, Moran received the Irish Presidential Service Award. He was singled out as a humanitarian, philanthropist and influential voice in the Irish peace process, who consistently championed reconciliation.
After Moran's death in 2018, former Secretary of State and 2016 Democratic presidential nominee, Hillary Clinton, was selected to succeed him as chancellor of Queen's University Belfast. She officially took office in January 2020.[5][6] In April, 2023, Queen’s University Belfast named its Graduate School The Thomas J. Moran Graduate School in Moran’s honor.