Mitchell was drafted by the
Phoenix Mercury twenty-fifth overall in the second round of
2008 WNBA draft. Mitchell was then traded to the
New York Liberty during the 2008 pre-season after the Liberty acquired Mitchell in a trade in exchange for a 2009 third round draft pick. Initially a bench player, Mitchell made her first professional start on 6 June 2008, in place of the injured Loree Moore. In her first career start against the Houston Comets she had team-high 18 points going perfect 6–6 from the floor including 3–3 from three-point range. During the 2008 season she developed a strong fan following and a reputation for fearlessness in grabbing loose balls and occasionally driving to the basket. Mitchell scored 14 points in the Liberty's narrow loss to the
Detroit Shock in Game 3 of the 2008 Eastern Conference Finals. Mitchell had a breakout year in the 2010 WNBA season. She became the regular starting point guard in the 2010 season, after the Liberty released Moore in the offseason. Mitchell averaged career-high 9.3 points and 3.8 assists per game. She scored 10-plus points 14 times, and lead the league in three-point field-goal percentage (48.6). Mitchell scored her first 20-point game against the Tulsa Shock. She won the 2010
WNBA Most Improved Player Award. On 2 September 2011, Mitchell scored a career-high 24 points in a win against the
Minnesota Lynx. On 21 April 2014, Mitchell announced that she was taking the
2014 WNBA season off to spend time with her family in Australia. As a result, on 7 August, the Liberty
waived Mitchell. On 4 February 2015, Mitchell signed with the Phoenix Mercury. On 12 June, versus the Indiana Fever, Mitchell scored then career-high 25 points, going 8–14 from the floor including 7–10 from three-point range. On 5 July, Mitchell hit the go ahead three-point shot in overtime with 3.9 seconds, in a 94–91 win over the Los Angeles Sparks. On 27 August, she scored 16 points and made a three-pointer from the top of the key at the horn to give Phoenix an 81–80 win over the Connecticut Sun. In 2016, Mitchell signed with the
Washington Mystics in the second half of the season to fill a roster gap at the point guard position. She played 10 games off the bench and averaged 5.9 ppg. In 2017, Mitchell returned to the Phoenix Mercury in free agency. On 23 May 2019, the Phoenix Mercury also waived Mitchell. After releasing Arica Carter and the standard 10 waiting period after Mitchell cleared all waiver, the Mercury resigned Mitchell on 5 June. On 28 June, Mitchell recorded her first career double double as she had 18 points and then career high 11 assists. On 30 July, against the Washington Mystics, she scored then career-high 28 points and tied a WNBA-record 8 threes in a single game. Against her former team the New York Liberty, Mitchell scored her career-high 29 points on 27 August. Mitchell ended the 2019 season averaging double figure points for the first time in her career as the Mercury finished 15–19 with the 8th seed in the league. The Mercury lost 105–76 to the Chicago Sky in the first round elimination game. Mitchell won the WNBA Most Improved Player Award, becoming the first player in either the NBA or WNBA to win the award twice. In February 2020, Mitchell signed with the Mystics in free agency. On 4 September, Mitchell recorded her second career double double as she had 20 points and career high 12 assists. She scored playoff career-high 25 points in the Mystics' loss to her former team Phoenix Mercury in the first round, losing the single elimination game 85–84. ==Career statistics==