Born in Charlotte, Jim grew up in Colts Neck Township, New Jersey where he attended Marlboro High School and was co-captain of both the basketball the golf teams.
2010 marked Jim's 20th consecutive season as lead play-by-play announcer for CBS Sports' NCAA men's basketball coverage. He has called play-by-play on more network broadcasts of the Final Four and championship game than any other announcer in the history of the tournament.
He also co-hosted NCAA Tournament and Final Four coverage for five years (1986-90) and was inducted to Naismith Memorial Basketball Hall of Fame as recipient of Curt Gowdy Media Award in 2002. Nantz was the winner of 1998's National Sportscaster of the Year Award and joined CBS Television Network in 1985 as host of college football studio show and currently serves as anchor of THE NFL TODAY.
He has hosted THE SUPER BOWL TODAY, CBS Sports' Super Bowl pre-game show for Super Bowl XXXV and XXXVIII and created and organized along with former president George Bush first-ever Super Bowl opening ceremony gala event and concert spectacular called Super Bowl XXXVIII - A Houston Salute, an event created to welcome world to Super Bowl. He has extensive credits credits at CBS include anchor of golf coverage, including The Masters and the PGA Championship, and primetime host of the 1998 Olympic Winter Games. He has called play-by-play for the U.S. Open Championships, NCAA track and field, skiing, speed skating baseball, swimming and diving, gymnastics, U.S. Olympic Festival and Pan American Games. Nantz also handled play-by-play duties for the regular and post-season coverage of THE NBA ON CBS (1986-89) and served as host of Network's coverage of the Macy's Thanksgiving Day Parade (1994, 1995, 2000 & 2001) and was co-host of weekend daytime coverage in 1992 and 1994 Olympic Winter Games, Cotton Bowl (1985-88), and the Heisman Trophy Award show (1986-88) and was lead play-by-play announcer for college football (1989-90) before moving on to cover the NFL (1991).
By 1993, he was the Network's No. 2 play-by-play announcer for the regular-season and post-season broadcasts. He returned as lead voice of college football in 1996 and moved into the studio in 1997 to anchor COLLEGE FOOTBALL TODAY. Nantz had a prominent role in 1996 Kevin Costner hit movie Tin Cup.
He earned a degree in broadcasting in 1981 from the University of Houston, where he played on the golf team and roomed with future PGA Tour players Fred Couples and Blaine McCallister. Nantz received honorary doctorate of humane letters degree from his alma mater in May 2001 in recognition of his contributions to his profession and the university. He held a variety of broadcasting jobs at Houston, leading to sportscaster positions at KHOU-TV and KTRH Radio. Nantz was also anchor at KSL-TV in Salt Lake City.
In May 2008, Jim published his first book entitled Always By My Side – A Father's Grace and a Sports Journey Unlike Any Other. In 2008, Jim also won tje Emmy Award for "Outstanding Sports Personality - Play-by-Play."
Jim and his ex-wife Ann-Lorraine "Lorrie" Carlsen Nantz have one daughter, Caroline. The Nantz' were married for 26 years before divorcing in 2009.