He has won two national championships, the 1999 and 2004 NCAA titles, as well as the 1988 NIT championship. In 2005, he was enshrined in the Basketball Hall of Fame.

Calhoun was born and raised in Braintree, where he was a standout on the basketball, football, and baseball teams at Braintree High School. After his father died of a heart attack when Calhoun was 15, he was left to take care of his large family, including five siblings.

Although he received a basketball scholarship to Lowell State (now UMass Lowell), he only attended the school for three months, after which he returned home to help support his mother and siblings. He worked as a granite cutter, headstone engraver, scrap yard worker, shampoo factory worker, and even grave digger.

After an 18-month leave from higher education, Calhoun returned to college, this time at American International College in Springfield, Massachusetts, where he was given another basketball scholarship. He was the leading scorer on the team his junior and senior seasons, and captained the team in his final year, during which AIC advanced to the Division II playoffs. At the time he graduated, he was ranked as the fourth all-time scorer at AIC. Calhoun graduated in 1968 with a bachelor's degree in sociology.

On February 3, 2003 Calhoun announced that he had been diagnosed with prostate cancer, two days after his worst home loss ever, a 24-point defeat to Boston College. He took an immediate leave of absence from the team and underwent surgery on February 6 to have his prostate removed. He was released from the hospital on February 9 and within days was back in the office, involved in the many day-to-day aspects of running the program. On February 22 Jim Calhoun returned to the sidelines for the team’s match-up with St. John’s at Gampel Pavilion, only 13 days after successful surgery to eliminate his prostate cancer.

Calhoun and his wife, Pat, live in Pomfret, Connecticut and have two sons and six grandchildren. They have been married since 1967. They have also purchased a $2.9 million dollar home on Long Island Sound in Madison, CT. The couple is well-known in Connecticut for their philanthropy, especially the Pat and Jim Calhoun Cardiology Center at the UConn Health Center and the annual Jim Calhoun Holiday Food Drive. Calhoun is also very active with Coaches Versus Cancer, the Boys and Girls Club, and the Children's Miracle Network, among other organizations. He has been the honorary chairman of the Juvenile Diabetes Foundation for over a decade.

Jim Calhoun began his coaching career at Lyme-Old Lyme High School in Old Lyme, Connecticut in 1968 after accepting a sixth grade teaching position in that town over the summer. After finishing 3-16 that season, Calhoun returned to Massachusetts after deciding not to complete the necessary certification paperwork to renew his teaching contract (he was certified in Mass. and working in Conn. only on a temporary certificate). After one season at Westport (Mass.) High, he accepted a position at Dedham High School and began building a very strong program. After completing a 21-1 season in 1972, Calhoun was quickly recruited by Northeastern University in Boston to serve as their new head coach. He took the position in October 1972, and quickly built Northeastern into the dominant power in the ECAC North Atlantic Conference. He also transitioned the team from Division II to Division I.

The team advanced to the Division I tournament 5 times under Calhoun. During his final three seasons, Northeastern achieved automatic bids to the NCAA tournament and had a 75-19 record. He received six regional Coach of the Year accolades at Northeastern and remains the institution's all-time winningest coach (248-137). Future Boston Celtics captain Reggie Lewis, who played for Calhoun at Northeastern, was a first-round NBA Draft pick in 1986.

On May 15, 1986, Calhoun was named the head coach at the University of Connecticut. After completing his first season just 9-19, Calhoun led the Huskies to a 20-14 record in 1988 and a bid to National Invitation Tournament. There they defeated Ohio State to win the NIT championship. In 1990, Calhoun was named the consensus National Coach of the Year after leading the Huskies to their first Big East championship, the NCAA Tournament Elite Eight, and a 31-6 record in only his fourth year at the helm.

Calhoun won his first NCAA national championship in 1999, as he led UConn to its first-ever Final Four and then championship game victory over Duke in St. Petersburg, Florida. The final score was 77-74 in UConn's favor as future NBA standout Richard "Rip" Hamilton led the team to victory.

Calhoun led the Huskies to another national championship in 2004, at the conclusion of a season that saw UConn start and complete the year as the number one team in the nation. UConn standouts Emeka Okafor and Ben Gordon were selected #2 and #3 in the NBA Draft, respectively. Calhoun now holds a 32-9 record with UConn in NCAA tournament play; they have never lost a First Round or Final Four game.

During the Jim Calhoun-era, the UConn Huskies have dominated the Big East Conference with an impressive 222-112 record (.665 winng pct.). The Huskies have won or shared conference titles in 1990,1994,1995,1996,1998,1999,2002, 2005,and 2006. UConn has also won six Big East Tournament championships, the last coming in 2004.

On March 15, 2005 he achieved his 700th win at Gampel Pavilion over Georgetown. His friend and Big East rival coach Jim Boeheim also won his 700th game during the previous week. Later in 2005, Coach Calhoun was honored by induction into the Dr. James Naismith National Basketball Hall of Fame. Calhoun's favored Huskies were defeated by George Mason in the 2006 NCAA Tournament.

Calhoun is also the only coach in NCAA history to have won at least 250 games at two different Division I schools.

Calhoun has faced some media attention for his decision to allow star point guard Marcus Williams to return in mid seaon in 2005-2006 following third degree felony charges against him.

A total of 16 players Calhoun has coached at UConn have gone on to play in the NBA. They are, from earliest to most recent: Clifford Robinson, Tate George, Chris Smith, Scott Burrell, Donyell Marshall, Kevin Ollie, Donny Marshall, Ray Allen, Travis Knight, Richard Hamilton, Khalid El-Amin, Jake Voskuhl, Caron Butler, Emeka Okafor, Ben Gordon, and Charlie Villanueva.