John J. “Jack” Koski

Chatham — John J. “Jack” Koski, 80, passed away peacefully on July 21, 2025, at Windsor Skilled Nursing and Rehabilitation.
Born in Attleboro, Massachusetts, he was the son of the late John J. Koski Sr. and Nova (Mitchell) Koski. Jack was predeceased by his stepson, Brian Carlson, whom he worked alongside and cared for deeply.
Jack shared 43 devoted years of marriage with his beloved wife, Sandra Koski, who passed away shortly after him in December 2025. Their bond and dedication to one another remained strong throughout their lives.
He leaves behind his brother, Robert Koski, along with his stepdaughter Jill Erickson, her husband Brad, and step-granddaughter Jinean of Jefferson, MA. Jack also cherished many special friendships throughout his life in the military, fishing community, the Town of Chatham, and his neighbors.
Jack spent much of his life in Central Massachusetts before eventually settling in Chatham, a place he loved. He dedicated many years to teaching and coaching at Paxton Center School, where he made a lasting impact on his students and community. A proud graduate of South High School and Worcester State, Jack was known for his strong work ethic and passion for the outdoors .
He was an avid lobsterman, who found great joy on the water on his fishing vessel he proudly called the “Sandy K”, after his wife, alongside with his step son Brian for many years. Upon retiring from that business, he served his community as Assistant Harbormaster with the Chatham ASSC.
Jack was a proud member of the VFW in Chatham. He served his country honorably as a Major in the United States Army Special Forces, a paratrooper, among other special duties and later retired after 28 years of service in the National Guard.
A man of deep faith, Jack carried his values with him throughout his life. He had a special love for animals, especially his dog, Seaweed, who was a constant companion. Jack will be remembered for his dedication to his wife, who he visited every day, his service to his country, and his love of the sea. He will be deeply missed by all who knew him.
There will be a joint burial with his wife Sandra Koski at the Bourne National Cemetery, on Friday May 1st 2026 at 1:15. There will also be Celebration of Life for Sandy, Jack and her son Brian Carlson at the VFW of Chatham MA on Saturday May 2nd 2026 from 2 to 4. Light refreshments will be served.
In Lieu of flowers donations may be made to the Alzheimer’s organization.