Bradford attended Putnam City North High School in Oklahoma City, Oklahoma, where he starred in football, basketball and golf. As a senior quarterback for his high school football team in 2005-2006, he threw for 2,029 yards and 17 touchdowns in 12 games. His senior year in basketball, he averaged a double-double.
However, Bradford was not that highly ranked among the high school class of 2006, ranked only 17th among quarterbacks by Scout.com and being overshadowed by the likes of Tim Tebow, Matthew Stafford and Mitch Mustain
In 2006, Oklahoma's starting quarterback Rhett Bomar, then a sophomore, was kicked off the team for violating NCAA rules. Paul Thompson, a senior quarterback-turned-wide receiver, converted back to quarterback and led the 2006 Oklahoma Sooners football team to win the Big 12 Championship Game. His departure left a void at the quarterback position at Oklahoma. That void would be filled by either true freshman Keith Nichol, redshirt freshman Sam Bradford, or junior Joey Halzle (the only one with game experience). On 2007-08-21, Bradford was named the starting quarterback for the 2007 Oklahoma Sooners football team.
In his first game for the Oklahoma Sooners on 2007-09-01 against the University of North Texas, Bradford completed 21 of 23 attempts for 363 yards and three touchdowns in just little over 2 quarters, breaking the school record for passing yards in a half, held by quarterback coach Josh Heupel, with 350. The very next game, Bradford broke Heisman Trophy winner Jason White's school record for most consecutive pass completions with 22 (18 came in the first half and four at the start of the second).
In the second week of the 2007 season, Bradford was named the national offensive player of the week by the Walter Camp Foundation after tying the school record for most touchdown passes in a game with five. Having thrown 25 TDs through his first nine games, Bradford is on pace to break the NCAA freshman record of 29 TDs set by David Neill in 1998 and tied by Colt McCoy in 2006.
In the November 17, 2007 game against Texas Tech, Bradford suffered a concussion of unknown severity. He was removed from the game and replaced by back-up quarterback Joey Halzle. The Sooners lost the game, 27–34. Bradford was able to play in the Bedlam game against Oklahoma State on November 24.
During the November 24, 2007 game against Oklahoma State Cowboys, Bradford broke the NCAA freshman record of 29 TDs by passing his 30th TD to Joe Jon Finley during the second quarter. At the Missouri game, Bradford threw for 209 yards and 0 interceptions. He was 18-26 and threw for 2 touchdowns. The Sooners won the Big XII Championship after defeating Missouri for the second time in a season. The Sooners played West Virginia in the Fiesta Bowl on January 2, 2008 and lost 48-28. It was Sam Bradford's first
BCS bowl as a starter.
St. Louis Rams
On April 22, 2010, Bradford was selected by the St. Louis Rams as the first overall pick in the 2010 NFL Draft. It was the first time the Rams selected a quarterback in the first round of a draft since the selection of Bill Munson in the 1964 NFL Draft. Bradford is the first No. 1 pick out of Oklahoma since Billy Sims was selected top overall by the Detroit Lions in the 1980 NFL Draft. Bradford chose the #8 in honor to Troy Aikman who also attended OU before transferring to UCLA.
On July 30, 2010, Bradford signed a six-year, $78 million deal, which has $50 million of guarantees and has a maximum value of $86 million making it the largest contract ever for an NFL rookie.
In the preseason opener against the Minnesota Vikings on August 14, Bradford went 6-of-13 for 57 yards and was also sacked 3 times in a Rams loss. After another unimpressive showing against the Browns in his second game, Bradford bounced back in a big way against the Patriots in the third game of the preseason. He got his first start in place of the injured A. J. Feeley, throwing two first half touchdowns and helping lead the Rams to a 36–35 victory.
He competed for the starting quarterback position with Feeley and on September 4, Bradford was named the starting quarterback for the 2010 season opener.
On September 12, 2010, in his first regular season game as the starting quarterback for the St Louis Rams, Bradford completed 32/55 passes for 253 yards, 1 touchdown and 3 interceptions.The Arizona Cardinals won 17–13. His first NFL touchdown came on a 1-yard pass to Laurent Robinson. Two weeks later, he then achieved his first victory as an NFL starter when the Rams defeated the Washington Redskins in an upset by a score of 30–16, which snapped a 13-game overall home losing streak. The next week, he passed for 289 yards and two TDs in leading the Rams over the Seahawks, 20-3. This was their first win in a division game since November 2007.
In week 8 against the Carolina Panthers, Bradford connected on 25 of 32 passes, two of them for touchdowns. In his first eight games he scored eleven TDs, which tied an NFL record—held by Dan Marino (1983), Peyton Manning (1998), and Ben Roethlisberger (2004)—for over that span by a rookie since the AFL–NFL merger in 1970. Bradford went 3-2 as a starter in October, passing for 1019 yards and 7 TDs against 3 INTs. He was named the NFL's offensive rookie of the month.
During October and November, he established a record for most consecutive passes without an interception for a rookie (169), which ended with an interception by William Moore in a home game against the Atlanta Falcons on November 21. On November 28, 2010, against the Denver Broncos, Bradford became the first rookie in NFL history to pass for at least 300 yards and three touchdowns with no interceptions during a road victory. He capped November by becoming the first rookie QB to win two consecutive Offensive Rookie of the Month awards.
On December 26, Bradford surpassed Peyton Manning's record for most completed passes by an NFL rookie quarterback (326). Bradford finished the season with 354 completions out of 590 attempts, therefore also surpassing Manning's record of 575 for most attempts by an NFL rookie quarterback. Bradford became just the third rookie quarterback to start all 16 regular season games and pass over 3000 passing yards, joining Peyton Manning and Matt Ryan.