Mortensen was born in Billings, Montana, to Sheryl and Don "Mort" Mortensen. He is the youngest of four, having three sisters, Dawn, Denise and Darcy. His father, Mort, was an electrician and his mother, Sheryl, has worked as a teaching assistant at the Lockwood Schools for over twenty-five years.
Mortensen developed a passion for rodeo at and early age and won his first team roping competition at the age of 6. By the age of 12 he had progressed through steer (age 10) up to riding bulls at the local youth rodeos. 
Mortensen attended Lockwood primary, elementary and junior high schools (k-8) from 1974 through 1984, and Billings Senior High (9-12) from 1985 through 1987. While attending Billings Senior High, Mortensen was an active member of the Future Farmers of America and competed in the Montana high school rodeo circuit.
During his Sophomore and Junior years at BSHS, Mortensen won the Montana High School Bull Riding Championship. Before graduating in 1987 he went on to win the Montana High School Saddle Bronc Championship and placed 2nd in the bull riding competition.
After graduation Mortensen accepted a scholarship to attend Northwest College in Powell, Wyoming. He spent two years on the Trapper rodeo team where he finished 2nd in the saddle bronc category to fellow future rodeo legend Ty Murray in both the College National Finals Rodeo and the Final National Standings for 1989. Mortensen then accepted a scholarship to Montana State University - Bozeman in Bozeman, Montana.
Mortensen joined the Pro Rodeo Cowboys Association (PRCA) in 1990. Placing 15th in the standings Mortensen was awarded the Rookie of the Year Award.
Mortensen followed up his rookie year in the PRCA by winning the National Intercollegiate Saddle Bronc Championship.
In 1992 Mortensen graduated from MSU-Bozeman with honors, earning a degree in Agri-business and Economics. The university later awarded Mortensen with its most prestigious award, The Blue and Gold Award, for his great lifetime service bringing international distinction to Montana State University - Bozeman.
Three years after joining the PRCA, Mortensen won the first of his six World Saddle Bronc Championships. He went on to win the saddle bronc titles in 1994, 1995, 1997, 1998 and 2003. His six titles ties him for most all time with the legendary cowboy Casey Tibbs.
In 1997 Mortensen was also the World's Top Cowboy by winning the World All-Around Rodeo Champion title.
During his 1998 run for the saddle bronc championship, Mortensen became the first rider in PRCA history to win over $200,000.00 in a single event. The following year Sports Illustrated named Mortensen one of Montana's top ten athletes of the century.
Mortensen claimed another first in rodeo history at the 2003 Pendelton, Oregon Round-up by becoming the first rough stock rider to exceed $2 million in career earnings.
Rodeo was included as a cultural event at the 2002 Winter Olympics in Salt Lake City, Utah. Mortensen participated on the U.S. team in competition agains the Canadian team. Mortensen took home the bronze medal for the competition.
The Montana Pro Rodeo Hall of Fame honored Mortensen in October of 2002 with the unveiling of an 18' statue of Dan riding the bronc Tee Box, as the center piece of their Wall of Fame monument at the Metra Park in Billings, Montana. The sculpture was the last work of western artist and fellow Montanan, R.F. Rains.
Montana State University - Bozeman inducted Mortensen into its Athletics Hall of Fame on September 17, 2004 at a ceremony in Bozeman.
At a ceremony in Colorado Springs, Colorado on July 9, 2009, Mortensen was inducted into the Pro Rodeo Hall of Fame.
- ↑ Dan Mortensen: six-time bronc-riding champion, Evelyn Boswell, The Montana State Collegian Vol. 81 No. 3, ISSN 1044-7717
- ↑ Sports Illustrated's Top Ten Montana Athletes of the Century, Sports Illustrated, December 27, 1999.
- ↑ 1993,1994,1995,1997,1998 World Saddle Bronc Riding Champion, Professional Rodeo Cowboys Association, Retrieved December 9, 2009
- ↑ 1997 All-Around Cowboy Championship, Professional Rodeo Cowboys Association, Retrieved December 9, 2009.
- ↑ Montana Almanac 2nd Edition, Andrea Merrill-Maker, Morris Book Publishing, LLC., 2006 ISBN 0-7627-3655-0
- ↑ 2003 World Saddle Bronc Riding Champion, Professional Rodeo Cowboys Association, Retrieved December 9, 2009
- ↑ Dan Mortensen, Montana Pro Rodeo Hall of Fame, Retrieved December 9, 2009
- ↑ Bobcat Hall of Fame All-Time Inductees, Montana State University, Retrieved December 9, 2009
- ↑ Mortensen headlines ProRodeo Hall of Fame inductions, Staff, Billings Gazette, July 11, 2009,
- ↑ Dan Mortensen walks contentedly into retirement, Joe Kusek, Billings Gazette, November 26, 2008
- ↑ Six-time world champion Dan Mortensen retires from ProRodeo, PRCA news release, ESPN, December 2, 2008.