In addition to A. J. Foyt and Rick Mears, he is the only one who could win the 500 miles of Indianapolis four times. He comes from a racing family, because his uncle Louis and Joe Our Prayer, as well as his brothers Bobby Unser and Jerry Unser, were racers. He is also the father of Al Unser, Jr. and the grandfather of Al Unser III, which are also racers.
1957 Al Unser began at the age of 18 years with the racing on oval courses in Albuquerque. He went into modified roadsters, Sprint or Midget cars at the start. In 1960 he started for the first time at the Pikes Peak International Hill Climb and was behind his brother Bobby in second.
His first start in the Indianapolis 500 was held in 1965. He finished the race in ninth, after he walked out of the last row in the race. This year at Pikes Peak, he celebrated his first victory in a Champ Car. In 1967 he was behind A. J. Foyt second in Indianapolis and took his first pole position in Langhorne. In 1968 he was in Nazareth, winning both races at the Indianapolis Raceway Park and the two runs in Langhorne five races in a row. He also began this season also five times from pole position and finished the season in third overall in the USAC National Championship. In 1969, he broke his leg in a motorcycle accident and was then unable to start in Indianapolis. In the course of the season he still won five races and was still second in the championship.
In 1970 he won the first time in Indianapolis, two years after his brother Bobby took his first win there. Al Unser dominated the race. He took pole position with a record speed of 170.221 miles per hour. In the race he led 190 of 200 laps. He won by a margin of 31.8 seconds before the Second Mark Donohue. This victory and that of his brother in 1968 made her the only brother pair that won the Indy 500. Even the championship for the first time he could decide for himself this year. With 10 wins and eight pole positions from 18 races he won superior from his brother Bobby the title.
In 1971 he was able to repeat his Indy 500 victory from last year. He was so by Wilbur Shaw, Mauri Rose and Bill Vukovich only the Fourth, who managed this. With a second place in 1972 behind Mark Donohue he missed the record of three Indy 500 victories in a row.
In 1978 he started in fifth Indy 500 On lap 75, he took over the lead for the first time and was able to race half up a lead of 23 seconds on Danny Ongais. As yet less than a third of the race before him, his lead had shrunk to 5.8 seconds. But after 362.5 miles died Ongais ' motor and Al Unser were able to celebrate his third win in Indy.
In the 1979 season he won a race and finished fifth overall in the new ChampCar Championship. In the following three seasons he won no races. Only after a move to Penske Racing in 1983 he was back in the winners track and decided the championship. He repeated this in 1985, when he was at his son Al Unser Jr. Champion by one point.
In 1987, he won five days before his 48th birthday for the fourth time in Indy. He started as a Twentieth. On lap 183, he took the lead and won 4.5 seconds ahead of Roberto Guerrero. He was thus the oldest winner of the 500- mile race. This record he took from his brother Bobby.
On 17 May 1994 Al Unser announced his retirement. To this day, he holds the record with the most laps led in Indianapolis.