Fisher was born in The Bronx, New York to Corey Wilson and Kiesha Fisher. Fisher grew up in the Castle Hill Houses, 14 tall brick buildings located in The Bronx. His father lived in a different building in the complex than Corey, his brothers, Ivan and Isaiah; and their mother. Fisher has said that he often spent time in the nearby playgrounds playing basketball, and was dubbed a "playground legend" after his 105-point game on August 7, 2010. Fisher was named after his uncle, Guy Fisher, ex-drug lord and former owner of the Apollo Theater in Harlem, New York City.
Fisher attended St. Patrick High School in Elizabeth, New Jersey, which was a two-hour commute from Fisher's home in The Bronx. "I looked around at everybody around me; I knew that if I didn’t get out of here, I’d never make it," Fisher said on his reason to attend school in New Jersey. As a Junior, Fisher averaged 14.9 points and 4.2 assists. Fisher was named New Jersey player of the Year by the Newark Star Ledger as a Senior and averaged 22.3 points, 6.1 rebounds and 8 assists. The Celtics went 30–2 and at one point were the number two team in the nation. In February of that year, Fisher led St. Patrick's to an overtime win against West Virginia's Huntington High School led by O. J. Mayo on national television. Fisher led the way with 37 points, while Mayo scored 47. Fisher would also play against current Villanova teammate Corey Stokes every year. Fisher closed his high school career with 16 assists in the annual Roundball Classic. Fisher was named an EA Sports All-American. He was also selected to the 2007 Jordan Brand Classic, in which he received MVP honors.
Fisher attended Villanova University and was a member on the basketball team as a Freshman under coach Jay Wright. During the 2007–08 regular season Fisher played every game except the opener against Stony Brook University due to tendonitis in his left knee. Fisher appeared in 34 games, while starting 21 of them. He ranked third on the team in minutes and averaged 9.1 points, 2.7 assists and 1.8 rebounds per game. Fisher produced 92 assists with committing 68 turnovers. He Connected on .354 of his attempts from the field (104–294), .331 from three-point range (41–124) and .747 at the foul line (59–79). Scored in double figures 14 times, including three games with at least 20 points. In Big East play, Fisher played all 18 games and started 14 of them. Fisher averaged 8.7 points, 2.7 rebounds and 2.2 assists per game. Fisher's season high for points came in a conference game against DePaul University on January 3, 2008 in which Fisher scored 23 points. His season high in rebounds came on February 20, 2008 against the West Virginia University. Assists came on February 25 against Marquette University.
On November 22, 2007, Fisher scored 18 points against the University of South Florida in the Old Spice Classic, and then followed that up with a 21-point game three days later against North Carolina State University.
Villanova was selected to play in the 2008 NCAA Tournament and advanced as far as the Sweet 16 versus the Kansas Jayhawks in Detroit, Michigan, in which Fisher scored 6 points along with 4 assists in the Wildcats' 72–57 loss.
As a sophomore during the 2008–09 regular season, Fisher played in all 38 games and made 12 starts.
On November 19, 2008, Fisher had 15 points, 6 rebounds and 5 assists against Niagara University.
On December 29, 2008, Fisher scored a season-high 23 points in a win over Temple University, a game in which he went .875 from the field, 4-of-4 from three-point range and .714 from the foul line.
On January 1, 2009, Fisher scored 21 points in a 79-72 loss to Marquette University.
On February 1, 2009, Fisher scored 11 points against the University of Cincinnati to begin a stretch of eight straight games scoring in double figures.
Fisher averaged 24.3 minutes per game and ranked third on the team in scoring at 10.8 points per game. He also averaged 2.3 rebounds and 2.8 assists per game. He had 107 assists along with 76 turnovers. Fisher was tied for second on the team with 47 steals while shooting .429 from the field, including .319 from three-point range, and .788 from the foul line. Fisher had 23 games scoring in double figures. He was named the Big East Conference Sixth Man of the Year.
In seven games between the Big East and NCAA Tournament, Fisher averaged 10.5 points, 3.4 rebounds and 3.0 assists per game to go along with 8 steals. He averaged 10.4 points and 4.2 rebounds during the NCAA Tournament alone. In the 2009 Elite Eight in Boston, Massachusetts, Fisher scored all seven of his free throws down the stretch to help Villanova defeat the University of Pittsburgh 78–76 to advance to the Final Four. Villanova won the game thanks to Villanova guard Scottie Reynolds's buzzer-beater layup with less than a second remaining on the clock.
On November 19, 2009, Fisher finished a 69–68 victory over George Mason University in the first round of the O'Reilly Auto Parts Puerto Rico Tip-off with 17 points and 6 rebounds; 14 of his points being on free-throws, a career high.
A day later, on November 20, Fisher scored 18 points, 10 of them free-throws, in a 71–65 victory at the University of Dayton.
On November 28, 2009, Fisher finished with a career high 6 steals along with 13 points and 4 assists in Villanova's 81–63 win over La Salle University.
On December 6, 2009, Fisher played a key role in Villanova's 95–86 win against the University of Maryland at the BB&T Classic, in which the Wildcats finished with 16 3-point shots made. He finished the night with a season-high 20 points; 4-of-6 from beyond the 3-point arc.
On December 13, 2009, Fisher contributed for 14 points to go along with 7 assists in a 75–65 loss at Temple University, Villanova's first loss of the season.
On February 6, 2010, Fisher became the 52nd Villanova player to reach 1,000 career points in a 103–90 win against Georgetown University.
During the 2010 NCAA Tournament, Fisher scored 9 points in the Wildcats' second-round game in which they were upset by St. Mary's College of California.
Fisher was named to the first team All-Philadelphia Big Five and third team All-Big East. He finished the season averaging 13.3 points, 3.9 assists and 2.8 rebounds.
Fisher returned to Villanova his senior year joined in the backcourt by sophomore Maalik Wayns and senior Corey Stokes.
Fisher scored 24 points in Villanova's first win of the season against Bucknell University on November 12, 2010.
Fisher scored 26 points along with 3 rebounds and 4 assists on November 24, 2010, to help the Wildcats defeat UCLA 82–70.
He was among the final ten candidates for the Bob Cousy Award.
On August 7, 2010, Fisher scored 105 points in a single organized summer league game. It is believed to be a new street basketball scoring record, surpassing Fly Williams's previous record of 100 set back in 1978. In the game, played at Watson Gleason Playground in The Bronx, New York City, Fisher scored 105 of his team's 138 points in a 138–130 victory over GymRatsNYC while shooting 23-for-28 from three-point territory.
In July 2011, he signed a one-year contract with Antalya BB in Turkey.
After one season in Turkey, Fisher signed in August 2012 for Spanish team Joventut Badalona.
On July 6, 2013, Fisher signed with Enisey Krasnoyarsk of Russia for the 2013–14 season.
After a season in China with Fujian Sturgeons, Fisher signed with KK Cibona in Croatia on July 28, 2015. He was released from Cibona in October 2015. On October 30, 2015, he signed with Guaros de Lara of the Venezuelan Liga Profesional de Baloncesto.
On September 1, 2016, Fisher signed with Lietuvos rytas Vilnius of the Lithuanian Basketball League. On May 24, 2017, it was reported that Fisher along with other American-born teammates Clevin Hannah and Taylor Brown were partying and consuming alcohol in Vilnius nightclubs right after losing the Game 3 of the LKL Playoffs on May 20. All of them were denying the fact but the incontestable pictures were published, which shattered all the doubts. The semi-final game was crucial as following it the series moved to Panevėžys and were lost 3–1, resulting in second shocking fiasco during the same season for the club. On the same May 24, all three players were suspended from the team. On May 25, head coach Rimas Kurtinaitis said that it was not the first time when all three players were behaving unprofessionaly and that they were ignoring previous warnings. Some witnesses noted that Taylor Brown previously was also consuming drugs.
On August 4, 2017, Fisher signed with San Pablo Burgos of the Spanish ACB League.