Following graduation, Sweeney returned to Montana and was a
high school assistant at his alma mater, Butte Central, for a season. He was its head coach from 1952 to 1955, then at
Flathead High School in
Kalispell from 1956 to 1959. Sweeney moved up to the college ranks in 1960 as an assistant coach at
Montana State in
Bozeman under
Herb Agocs, and was promoted to head coach in 1963. He compiled a record and three
Big Sky Conference championships in his five seasons with the Bobcats, where one of his starting
quarterbacks was
Dennis Erickson. Sweeney's salary at MSU in 1967 was
$15,000. Stenerud went on to become the only "pure" kicker inducted into the
Pro Football Hall of Fame. After his success in Bozeman, Sweeney moved up to the
Pac-8 Conference at
Washington State in
Pullman, He had only one winning season (
1972) and compiled a record in eight seasons. His team's most noteworthy accomplishment was the defeat of
Rose Bowl-bound
Stanford in
1971 to garner him NCAA District 8 Coach of the Year honors. One of his notable hires in Pullman was WSU alumnus
Jack Elway, father of future hall of fame quarterback
John Elway. After a disappointing conclusion to the
1975 season (winless in conference), Sweeney resigned at WSU a week after the season ended. Promptly hired at
Fresno State, Sweeney led the Bulldogs for two seasons before becoming a
National Football League (NFL) assistant for two years. He spent the season with the
Oakland Raiders in
John Madden's final and the season with the
St. Louis Cardinals under
Bud Wilkinson, who was fired before the season's end. Sweeney returned to Fresno State as head coach in December
1979 for 17 more seasons; he compiled a record and eight conference championships (
PCAA/Big West and
WAC) in 19 seasons. Sweeney retired from coaching following the
1996 season with 201 wins in 32 seasons. He was most proud of the
1977 team (9–2), and credited them as the "stadium builders", because their success got the local community motivated to fund and construct
Bulldog Stadium, which opened in
1980. ==Personal life==