Murphy was born in Bronxville, New York and grew up in Yorktown Heights, New York, the youngest of six children. His father was a union leader with UWUA 1-2 who worked for Con Edison. Murphy decided to study chiropractic following his graduation from high school, and received a Bachelor of Science in Nutrition and a Doctor of Chiropractic from what was then Life Chiropractic College.
In 1999, he opened his own medical practice, Yorktown Health and Wellness Center, in his hometown of Yorktown. In addition to his chiropractor's office, for the next fifteen years, he served as an on-field volunteer medical advisor for local high school athletes. In 2006, along with his siblings, he opened a family restaurant, Murphy's Irish Restaurant and Bar, named in honor of his father.
He is married, with three children. His wife is a nurse. Together they founded a watchdog organization, Keeping Westchester Safe, which advocated for "Child Safety Zone" legislation, residency requirements for sex offenders that would prohibit them from residing within a certain distance of schools, playgrounds and other areas where children congregate.
In 2009, Murphy ran for and was elected to the Yorktown Town Board and was re-elected for a second term in 2013. He had a run close race for the Westchester County Board of Legislators in 2011, which went to a recount. Murphy and his fellow council members were credited with approving more than $300 million in long-awaited economic development projects within the town, many of which had stalled for years under previous administrations, including a $60 million overhaul of the Jefferson Valley Mall and the redevelopment and widening of the Route 202 corridor.
During his local races, he was the top vote-getter in the town of Yorktown and received the highest ever number of votes cast for a town council member in 2013. As a local councilman, he was tapped to serve on both the New York State Assembly Task Force on Crime on Our Communities, also known as the Sex Offender Watch Task Force, as well as the Senate Task Force of Heroin and Opioid Addiction. In 2014, he was tapped to succeed Senator Greg Ball, who had decided not to run for re-election.
The suburban seat was targeted by New York City Democrats including Mayor Bill de Blasio, who funneled over $500,000 to Murphy's opponent through the use of straw donor committees using a loophole in New York State campaign finance law. The move allowed a few donors to give contributions far in excess of the legal limit to evade the cap that would have otherwise applied. It was also alleged that de Blasio pressured donors with business before the City to make the donations to Murphy's opponent on his behalf, which made one donor feel "uncomfortable." The Mayor also sent staff to work on the campaign of Murphy's opponent. In turn the election was cast by Murphy as a battle of New York City interests against those of Hudson Valley, with de Blasio portrayed as something of a "bogeyman" according to the Journal News.
Although the race was hotly contested and was expected to be one of the closest in the State, Murphy handily defeated his opponent in a decisive victory by over ten points.
He took office in January 2015. Murphy was named the chair of the Administrative Regulations Review Commission, an entity charged with reviewing proposed rules and regulations by State agencies and public authorities to examine their compliance with legislative intent and their potential impact on businesses and local governments. The Senator was also named to the Banks, Ethics, Labor, Local Government, Health, Investigations and Government Operations, and Mental Health committees.
Murphy named combating heroin addiction and prescription drug abuse as a top priority for his first senate term.