One year later, he moved to Fresno, California, where he would spend the rest of his childhood and then attended San Joaquin Memorial High School.

While at San Joaquin High School he played basketball with his twin brother, Robin Lopez, and Quincy Pondexter, both fellow future NBA players.

Both teammates played with Lopez on their successful AAU team, the Elite Basketball Organization (EBO), along with Derrick Jasper and Tre'Von Willis, both of UNLV.

In the second round of the 2008 NCAA tournament, Lopez hit the game-winning shot at the buzzer against the Marquette Golden Eagles for an 82–81 overtime victory.

Despite his improving play, however, the Nets struggled all season, finishing with one of the worst records in NBA history at 12–70; only 3 more wins than the 1972–73 Philadelphia 76ers.

In the preseason of the lockout-shortened 2011–2012 campaign, Lopez broke his right foot and missed the first 32 games of the regular season.

[21] On December 20, 2013, the Nets announced Lopez was out for the remainder of the season with a foot injury he had suffered the night before against the Philadelphia 76ers.

[22] In the 17 games that Lopez played, he averaged 20.7 points 6 rebounds, shot 56.3% from the field and 81.7% from the free throw line.

He remained coming off the bench for three more games before starting alongside Plumlee on December 30 against Chicago with Kevin Garnett out resting.

[26] On March 20, 2015, Lopez recorded 32 points and a season-high 18 rebounds in a 129-127 triple overtime win over the Milwaukee Bucks.

[31] On December 26, in a loss to the Washington Wizards, Lopez made nine field goals and passed Vince Carter (3,126) for second in franchise history.

Lopez finished the game with 3,127 career field goals made, a mark trailing only Buck Williams (3,981).

[33] Two days later, he was named Eastern Conference Player of the Week for games played Monday, December 28 through Sunday, January 3.

[38] During the offseason, Nets coach Kenny Atkinson told Lopez to be ready to become a three-point shooting specialist during training camp.

[46] On March 26 against Atlanta, Lopez became the Nets' career leader in field goals, passing Buck Williams.

[47] With 25 points against the Boston Celtics on April 10, Lopez passed Williams to become the franchise's career leading scorer.

[48] On June 22, 2017, Lopez was traded, along with the rights to Kyle Kuzma (the 27th pick in the 2017 NBA draft), to his hometown team the Los Angeles Lakers in exchange for D'Angelo Russell and Timofey Mozgov.

[49] In his debut for the Lakers in their season opener on October 19, 2017, Lopez scored 20 points in a 108–92 loss to the Los Angeles Clippers.

[60] In Game 1 of the Eastern Conference Finals, Lopez scored a playoff career-high 29 points to lead the Bucks to a 108–100 win over the Toronto Raptors.

[62] He made his season debut for the team on October 24, 2019, logging 11 points, 3 assists, and 5 blocks in a 117–111 win over the Houston Rockets.

[68] On December 23, 2020, Lopez made his season debut for the Bucks, recording seven points, three rebounds, and two blocks in a 122–121 loss to the Boston Celtics.

[70] In Game 5 of the Eastern Conference Finals against the Atlanta Hawks, Lopez put up a new post-season career high 33 points to lead the Bucks to a 123–112 victory.

Lopez made his season debut for the Bucks on October 19, 2021, where he logged eight points, five rebounds, and three blocks in a 127–104 win over the Brooklyn Nets.

[75] Lopez made his return on March 14, 2022, where he recorded 6 points, 1 rebound, 1 assist, and 1 steal in a win against the Utah Jazz.

On April 5, Lopez had a team-high 28 points and 3 blocks in a 127–106 win as the Bucks swept the Chicago Bulls in the regular season.

[79] On March 9, 2023, Lopez recorded a career-high nine blocks, while adding 24 points and 10 rebounds, during a 118–113 win over the Brooklyn Nets.

[83] During the playoffs, Lopez finished second in voting for Defensive Player of the Year, and was named for the first time to the NBA All-Defensive First Team.

[86] On November 24, Lopez tied his career-high with 39 points on 14-of-17 shooting, 4-of-7 from three and 7-of-7 from the free throw line in a 131–128 win over the Washington Wizards.

[87] On April 29, 2024, during the NBA playoffs, Lopez scored a team-leading 27 points and grabbed nine rebounds during a 126–113 Game 4 loss to the Indiana Pacers.

Alex played college basketball for Washington and Santa Clara,[90] and professionally in Japan, New Zealand,[91] and Spain.