John M. Day, of Norwood, MA, formerly of South Boston, passed away peacefully, surrounded by the love, comfort, and care of his devoted family, at the Residence at Salem Woods in Salem, New Hampshire. He was the beloved husband of the late Bridget T. (McDonough) Day, who passed away on September 11, 2021.

Born in Boston, John was the son of the late Walter M. Day and Anna (Quigley) Day. He was raised in South Boston and graduated from South Boston High School. John continued his education by earning his bachelor’s degree and master’s degree in education from Boston State College.

For over 30 years, John dedicated himself to teaching biology at West Roxbury High School. He took great pride in his profession and in the countless students he educated and inspired throughout his long and meaningful teaching career.

Outside of his work, John found joy and relaxation on the fairways and greens of local golf courses, and he especially enjoyed listening to Irish music.

John is survived by his beloved children, Sean M. Day and his wife, Caitlin, of Kingston, MA, and Courtney D. Matheson and her husband, Kevin, of Billerica, MA. He was a devoted and loving grandfather to Gwendolyn. John was predeceased by his beloved brothers, James Day and William Day.

John is also survived by many cherished nieces, nephews, in-laws, and extended family members.

John’s Funeral Mass will be celebrated on Thursday, April 30, 2026, at 11:00 a.m. at St. Catherine of Siena Parish, 547 Washington Street, Norwood, Massachusetts. Relatives and friends are kindly requested to meet directly at the church.

Interment will follow at Knollwood Memorial Park in Canton, where John will be laid to rest alongside his beloved wife.

At the request of the family, kindly omit flowers. Memorial contributions in John’s name may be made to the Joslin Diabetes Center, Office of Philanthropy, 529 Main Street, 4th Floor, Charlestown, MA 02129, or online at the Joslin Diabetes Center website:Joslin Diabetes Center - Beth Israel Lahey Health