***Please note, visiting hours will now be held in St. Lawrence Church on Tuesday instead of the funeral home***

O'Brien, Thomas F., M.D., of Brookline passed away peacefully on December 9th, 2024, at age 95. Beloved husband of sixty-six years to Ruth (Reardon) O'Brien, Esq. Loving father of Neal O'Brien of Brookline, MA, Luke O'Brien and his wife Ilse (Martin) O'Brien of Holliston, MA, Conan O'Brien and his wife Liza Powel O'Brien of Los Angeles, CA, Kate O'Brien of Boston, MA, Jane O'Brien of San Anselmo, CA, and Justin O'Brien and his wife Joanna Shea O'Brien of Winchester, MA. Devoted grandfather to his nine grandchildren. He is also survived by his sister-in-law Judith (Colognesi) O'Brien and fifteen nieces and nephews. Predeceased by his parents Francis Noonan O'Brien and Gertrude (Connor) O'Brien, as well as his siblings Kathleen and David O'Brien.

Dr. O'Brien was born in Worcester, MA, and grew up in Millbury and Southbridge, MA. Dr. O'Brien was a graduate of Mary E. Wells High School, Southbridge, MA (1946), College of the Holy Cross, Worcester, MA (A.B. magna cum laude, Classics,1950), and Harvard Medical School, Boston, MA (M.D. cum laude with full scholarship, 1954).

Dr. O'Brien was a Resident, Department of Medicine, Peter Bent Brigham Hospital, Boston, MA (1954-56), a Mosley Traveling Fellow in Immunology, Cambridge University, United Kingdom (1956), Captain, U.S. Army Medical Corps, Brook Army Medical Center, San Antonio, TX (1957-59), and Research Fellow, Department of Microbiology, Harvard Medical School (1959-1961).  During the following thirty years, Dr. O'Brien was Director of the Division of Infectious Diseases and Director of the Microbiology Laboratory, Peter Bent Brigham Hospital (later Brigham & Women's Hospital), Boston, MA (1962-1992) and served as an Associate Professor, Harvard Medical School. Dr. O'Brien was a resident of Brookline since 1963.

A Funeral Mass will be celebrated on Wednesday morning December 18th at 11:00 in St. Lawrence Church, 774 Boylston St., (Route 9 East) Chestnut Hill. Visiting hours will be held in the church on Tuesday December 17th from 3:00 – 7:00. Relatives and friends are kindly invited. Interment will follow in Walnut Hills Cemetery.

In lieu of flowers, please consider making a donation in memory of Dr. Thomas F. O'Brien, Class of 1950, to College of the Holy Cross, P.O. Box DEV, 1 College Street, Worcester, MA 01610, or to The Michael J. Fox Foundation for Parkinson's Research, P.O. Box 5014, Hagerstown, MD 21741.