In three seasons with the Sacramento Kings, Wallace rarely played, but in his brief appearances, he made himself known for his versatility and extraordinary athleticism. In the 2002 Slam Dunk Contest, Wallace finished second to two-time winner Jason Richardson. During his tenure with the Kings, Wallace was the odd man out in a deep roster that included All-Stars Chris Webber, Peja Stojaković, Vlade Divac, Hedo Türkoğlu and Brad Miller.

Wallace was known for his somewhat reckless style of play that led to his frequent injuries and earned him the nickname “Crash”. He missed a total of 39 games in his first two years with the Bobcats, but his energetic and sometimes dangerous behavior that may have caused his injuries was also what contributed to his gaudy defensive stats. Coach Bernie Bickerstaff said of Wallace, “Gerald can only play one way and be effective. Energy — that’s his game.” In 2006, Wallace attempted to refine his game in order to avoid being injured, and as a result his numbers suffered. The first month of the season, Wallace had only five total blocks (an average of .3 per game) and his averages were down across the stat line from 2005. Wallace improved his play in the second month of the season, but he went down with a separated shoulder in a December game against the Indiana Pacers. When he returned, Wallace continued his fine play finishing the season averaging 18.1 points, 7.2 rebounds, 2.6 assists, 2 steals, and 1 block in 72 games.

Wallace suffered a Grade 3 concussion on February 23, 2008 after taking an unintentional elbow to the face from Sacramento’s Mikki Moore. It was his fourth concussion in as many seasons with the Bobcats. It was not clear when he would return, although Grade 3 concussions are defined by the American Association of Neurological Surgeons as ones that “involve post-traumatic amnesia for more than 24 hours or unconsciousness for more than five minutes. Players who sustain this grade of brain injury should be sidelined for at least one month, after which they can return to play if they are asymptomatic for one week.” He returned later on in the season, finishing the year with a new career high in points, assists, and minutes.

He suffered a partially collapsed lung and a fractured rib after being flagrantly fouled while driving for a layup by Los Angeles Lakers’ Andrew Bynum on January 27, 2009 and was forced to miss seven games. He also was unable to fly and instead crossed the United States en route back to Charlotte by bus.

Wallace was selected to play in the 2010 NBA All-Star Game in Dallas, becoming the first and only Charlotte Bobcat to do so (with the Bobcats changing their name back to their original Hornets name after reclaiming the Charlotte NBA history originally owned by the Pelicans franchise in 2014). Wallace was also selected to participate in the 2010 NBA All-Star Weekend Slam Dunk Contest. He was also selected to the 2010–2012 USA Basketball Men’s National Team to represent the United States in the 2010 FIBA World Championship along with a possible trip with the team to the 2012 Olympics.

In 2010, Wallace was named to the NBA All-Defensive First Team. During the 2010–2011 season as a Bobcat, he averaged 15.6 points per game, 8.2 rebounds per game, and 2.4 assists per game in 39 minutes per game. He played 48 games with the team during the season.

On February 24, 2011, Wallace was traded to the Portland Trail Blazers for Joel Przybilla, Dante Cunningham, Sean Marks, and two future draft picks. He provided help for the team while Brandon Roy was injured. The Trail Blazers finished 48-34, good for the playoffs. They lost in the opening round to the Dallas Mavericks in 6 games. In the next season as a Trail Blazer, Wallace averaged 13.3 points per game, 6.6 rebounds per game, and 2.7 assists per game in 35.8 minutes per game. He played 42 games with the team that season.

On March 15, 2012, Wallace was traded from the Portland Trail Blazers to the New Jersey Nets in exchange for Shawne Williams, Mehmet Okur and a 2012 top-3 protected 1st round draft pick. On April 8, 2012, Wallace injured his left leg on a put back dunk. Wallace would only play 2 more games the entire season. Wallace played in 16 total games for the Nets that season and averaged 15.2 points per game. On July 11, 2012, Wallace re-signed with the Nets. The contract is reportedly worth $40 million for four years. In the first game of the season Wallace injured his left ankle. With just 27 seconds left on the game clock, Wallace got hurt trying to block a shot by Raptors point guard Kyle Lowry. After the game the team announced it was a sprained left ankle. Wallace would miss 6 games before making his return. Wallace would get injured again when the Nets played the Phoenix Suns on January 11, 2013. Wallace injured his ribs after the Phoenix Suns player P. J. Tucker fouled him hard while attempting a fast break dunk early in the first quarter. Wallace landed awkwardly on the floor and remained on the court for several moments before being helped to get on his feet and to the locker room. He did not return to the game. Wallace would miss 2 games until he returned to play the Atlanta Hawks.

Wallace was traded to the Boston Celtics on July 12, 2013, in a multi-player deal that sent Kevin Garnett, Paul Pierce, and Jason Terry to the Nets.

On February 28, 2014, Wallace was ruled out for the rest of the season after an MRI revealed a torn meniscus in his left knee.

On July 27, 2015, Wallace was traded, along with Chris Babb, to the Golden State Warriors in exchange for David Lee. Four days later, Wallace was traded to the Philadelphia 76ers, along with cash and draft considerations, in exchange for Jason Thompson. On September 27, 2015, he was waived by the 76ers.