James was selected by his hometown team, the Cleveland Cavaliers, as the first overall pick of the 2003 NBA draft.

In his first regular season game, he scored 25 points against the Sacramento Kings, setting an NBA record for most points scored by a prep-to-pro player in his debut performance.

At the conclusion of the season, he became the first Cavalier to receive the NBA Rookie of the Year Award,and with final averages of 20.9 points, 5.5 rebounds, and 5.9 assists per game, he also became just the third player in league history to average at least 20 points, 5 rebounds, and 5 assists per game as a rookie.

Cleveland ultimately finished the season 35–47, failing to make the playoffs despite an 18-game improvement over the previous year.

At the conclusion of the 2008–09 season, James finished second in NBA Defensive Player of the Year Award voting and made his first NBA All-Defensive Team,posting 23 chase-down blocks and a career-high 93 total blocks.

In the playoffs, Cleveland swept the Pistons and the Atlanta Hawks to earn a matchup with the Orlando Magic in the Conference Finals.

In February of the 2009–10 season, James was forced into a temporary point guard role following a series of injuries to players in the Cavaliers' backcourt.

The Cavaliers were officially eliminated from the postseason in Game 6, with James posting 27 points, 19 rebounds, 10 assists, and nine turnovers in the losing effort.

James was humbled by the Heat's loss to the Mavericks, and the experience inspired him to leave behind the villain role that he had been embracing, which helped him regain a sense of joy on the court.

In the second round of the playoffs, Miami temporarily lost Chris Bosh to an abdominal injury and found themselves trailing the Indiana Pacers 2–1.His full postseason run, in which he averaged 30.3 points, 9.7 rebounds, and 5.6 assists per game, was later ranked the second best in modern NBA history by ESPN.

In February of the 2012–13 season, James averaged 29.7 points and 7.8 assists per game while setting multiple shooting efficiency records.His final season averages were 26.8 points, 8 rebounds, 7.3 assists, and 1.7 steals per game on 56.5 percent shooting.

In Game 1 of the Conference Finals, James scored a buzzer-beating layup to give Miami a one-point victory against the Pacers.He was named Finals MVP for the second straight season, averaging 25.3 points, 10.9 rebounds, 7 assists, and 2.3 steals per game for the championship round.

In January of the 2014–15 season, James missed two weeks due to left knee and lower back strains, which represented the longest stretch of missed games in his career.

During the 2015–16 season, James was criticized for his role in several off-court controversies, including the midseason firing of Cavaliers' coach David Blatt.

On June 29, 2018, James opted out of his contract with the Cavaliers and became an unrestricted free agent.On July 1, his management company, Klutch Sports, announced that he would sign with the Los Angeles Lakers;the deal was officially completed on July 9.

The Lakers expected James to make them championship contenders again after having missed the playoffs since 2014 and not appearing in the Finals since 2010.Following his signing, the team rounded out their roster with a controversial collection of playmakers and veterans. As a result, to begin the 2018–19 season, the team struggled to find effective lineups and recorded only two wins through their first seven games.James's final averages were 27.4 points, 8.5 rebounds, and 8.3 assists per game, and despite his inconsistent campaign, he was ultimately named to the All-NBA Third Team, marking the first time in 12 years that he did not make the All-NBA First Team.

On December 2, 2020, James signed a two-year $85 million extension, signing with the Lakers through the 2022–23 season.

During the offseason, the Lakers hired Frank Vogel as their new head coach, and traded the majority of their young core to the Pelicans for superstar big man Anthony Davis.James immediately embraced Los Angeles's much-improved roster by transforming his playing style, moving to full-time point guard and competing with a more consistent defensive effort.

The Lakers entered the playoffs as the number one seed in the West and advanced to the Finals convincingly, with only three total losses along the way. In Game 5 of the Conference Finals against the Nuggets, James helped clinch the conference championship by scoring a game-high 38 points, including 16 in the fourth quarter.

The 2016–17 season was marred by injuries and unexpected losses for the Cavaliers;James later described it as one of the "strangest" years of his career.Following a January defeat to the New Orleans Pelicans, he publicly criticized Cleveland's front office for constructing a team that he felt was too "top heavy", for which he received countercriticism.The Cavaliers finished the season as the East's second seed, with James averaging 26.4 points and career highs in rebounds (8.6), assists (8.7), and turnovers (4.1) per game.

Prior to the start of the 2017–18 season, the Cavaliers overhauled their roster by trading Kyrie Irving to the Celtics, who requested a trade in part because he no longer wanted to play with James.

On June 25, 2014, James opted out of his contract with the Heat, and on July 1, he officially became an unrestricted free agent.On July 11, he revealed via a first-person essay in Sports Illustrated that he intended to return to the Cavaliers.In contrast to The Decision, his announcement to return to Cleveland was well received.On July 12, he officially signed with the team,who had compiled a league-worst 97–215 record in the four seasons following his departure.A month after James's signing, the Cavaliers acquired Kevin Love from the Minnesota Timberwolves, forming a new star trio along with Kyrie Irving.

On March 3 of the 2013–14 season, James scored a career-high and franchise-record 61 points in a game against the Charlotte Bobcats.

For the Finals, James averaged 28.2 points, 7.8 rebounds, and 2.0 steals per game.

James officially signed with the Heat on July 10, 2010.As part of the first player-created NBA superteamhe became only the third reigning MVP to change teams and the first since Moses Malone in 1982.

Throughout the 2010–11 season, the media and opposing fanbases treated James and the Heat as villains.To begin the year, they struggled to adjust to these new circumstances, going only 9–8 after 17 games.

In the conference semifinals, James and his teammates found themselves matched up with the Celtics for the second consecutive year.His Finals scoring average of 17.8 points per game signified an 8.9-point drop from the regular season, the largest point drop-off in league history.

James became an unrestricted free agent at 12:01 am EDT on July 1, 2010.[78] During this time, he was contacted by several teams, including the Bulls, Los Angeles Clippers, Miami Heat, New York Knicks, New Jersey Nets, and Cavaliers.

As a result of his actions during the 2010 free agency period, he quickly gained a reputation as one of America's most disliked athletes, which was a radical change from prior years.The phrase "taking my talents to South Beach" became a punch line for critics.In retrospect, James has expressed some regret over his handling of The Decision.

James earned his first NBA All-Star Game selection in 2004–05, contributing 13 points, 8 rebounds, and 6 assists in a winning effort for the Eastern Conference.

At the 2006 All-Star Game, James led the East to victory with 29 points and was named the NBA All-Star Game Most Valuable Player.

In 2006–07, James's averages declined to 27.3 points, 6.7 rebounds, 6 assists, and 1.6 steals per game.

In February of the 2007–08 season, James was named All-Star Game MVP for the second time behind a 27-point, 8-rebound, and 9-assist performance.