Frederick Robert O’Brien Jr., 86, of Marlborough, passed away unexpectedly at home on December 12, 2025. He is survived by his loving wife of 64 years, Dorothy (Dolan) O’Brien.

Frederick was born on June 15, 1939, in Boston and raised in Norwood. He was the son of the late Frederick R. O’Brien, Sr. and Anne E. (Chaisson) O’Brien. He was predeceased by his brother David J. O’Brien.

Frederick received his undergraduate degree in mechanical engineering from Tufts University and then earned a master’s degree in engineering from Northeastern University. An engineer and then engineering manager, he was employed for many years by Honeywell Corporation and Digital Equipment Company before retiring in 2000. An avid photographer, you would find Fred behind the camera at every family or sporting event. Fred expressed his creativity through the making of beautiful stained-glass pieces. His passion for woodworking resulted in the establishment of Apple Valley Woodworks, a company under which he sold various toys, stools, and furniture. His mantel clocks, Christmas decorations, and one-of-a-kind children’s toys are precious gifts that his family and friends will cherish and pass on for generations.

Frederick is survived by his children, Dr. Daniel O’Brien and his wife, Dr. Mary O’Brien, of Southborough, William O’Brien and his wife, Aine, of Mount Pleasant, South Carolina, and Elizabeth O’Brien of Bourne. He also leaves behind his grandchildren, Daniel O’Brien (Sarah) of Milford, Sean O’Brien of Dayville, CT, Molly O’Brien of Boston, Patrick O’Brien of Southborough, Harry O’Brien of Bourne and his great grandson, Jack O’Brien. Also left behind are his sisters-in-law, Elizabeth Landers and Roberta Dolan. He also leaves behind his nephew Derek O’Brien of San Diego, CA along with multiple other cousins and nephews.

Visiting hours for Frederick will be held on Thursday, December 18, 2025, from 5:00-7:00pm at the Slattery Funeral Home Inc., 40 Pleasant Street, Marlborough, MA 01752. A funeral Mass will be celebrated Friday, December 19, 2025 at 10:00am at St. Anne Church, 20 Boston Post Road, Southborough, MA 01772. Burial will be held at a later date. In lieu of flowers, the family requests donations be made to Globe Santa, www.globesanta.org.