Tom's father was born in Italy, and his mother was born in Queens. He is a first-generation American who grew up in Glen Cove and, with his wife Helene, has raised their three children there. Tom's maternal grandfather, a member of Local 3 IBEW for almost 50 years, put the lights on the top of the Empire State Building. His mother was a nurse, and his father, at 28, was the youngest judge ever elected in the history of New York State.

Tom graduated from Chaminade High School, Boston College, and Fordham University School of Law. At Fordham, his volunteer work in the soup kitchen at the Church of St. Paul the Apostle helped unleash a wave of student interest in public service, which led to the Fordham Law School's Public Service Project, which lives on to this day.

Tom was elected as mayor of Glen Cove 30 years ago, where he is credited with a dramatic turnaround in his hometown. The New York Times wrote that Tom had "done more to revitalize [Glen Cove] and reinvigorate its flagging economy in a few short years than the last several mayors combined." In 2001, Tom was elected Nassau County Executive, inheriting a county that had been rated "the worst-run county in the country." Tom was named Governing Magazine's Public Official of the Year and was described as "the man who spearheaded Nassau County, New York's remarkable turnaround from the brink of fiscal disaster." As Nassau County Executive, Tom oversaw the 12th largest police department in the country. During his tenure, Nassau's crime rate was reduced drastically and was rated the safest community over 500,000 in the United States. Tom was also named New York State's Environmentalist of the Year by the League of Conservation Voters for his environmental work.

In 2016, Tom was elected to Congress and continued his record of getting things done and delivering for his constituents. In their 2020 endorsement of his reelection, Newsday described Tom as "the relentless voice Long Island needs in Washington" crediting him for leading the effort to reduce taxes, protect the environment, and improve infrastructure on Long Island. He served on the powerful Ways & Means Committee as well as the Committees on Foreign Affairs and Armed Services.

Tom focused on bipartisanship and was the Vice Chair of the Problem Solvers Caucus, which is composed of 25 Democrats and 25 Republicans who meet every week to try and find common ground. In that role, he helped negotiate the historic Infrastructure and Jobs Act, which invested billions of dollars to improve New York's infrastructure.

In 2019, he co-authored a New York Times opinion piece with Republican Congressman Peter King titled "A Grand Compromise on Immigration." Their approach strengthens security at the border, stops the abuse of the asylum program, better screens immigrants for security risks while creating a path to earned citizenship for immigrants who work hard, follow the law and pay taxes.

Tom understands how expensive it is to live on Long Island and in Congress he worked tirelessly to bring federal funds back to Nassau and Queens, increasing funding by almost 500% for the Long Island Sound, securing millions for the Bethpage Water District, and leading a bipartisan effort for New York State to get its fair share of federal funds during Covid. Tom also passed legislation to lower the cost of insulin and other prescription drugs. Tom and his wife Helene reside in Glen Cove. They have three children, Caroline, Joseph, and Michael, and a family dog, Gabby.