After two years with Charlton Athletic from 2004, Chapman joined Arsenal Ladies and reached prominence with the team in her first season, winning a domestic treble as well as the UEFA Women's Cup.

A two-time winner of the FA International Player of the Year in 2002 and 2010, Chapman took a break from the national team in March 2011 with a total of 82 caps and eight goals.

[6] Lou Waller, who scored Millwall's winning goal in the FA Women's Cup final victory over Wembley, had been Chapman's coach in the club's youth teams.

[11] In 2001–02 Chapman helped Fulham win the FA Women's Premier League Southern Division and promotion to the top flight.

She also scored two goals in the 7–1 Premier League Cup final win over Birmingham City, after which Fulham's manager Gaute Haugenes claimed Chapman was good enough to play in any national side in the world.

[12] Chapman then scored the winning goal in the 2–1 FA Women's Cup final victory over Doncaster Belles, a volley from 20 yards.

She made the announcement during half-time of a match against Tranmere Rovers, and was promptly substituted by Haugenes – who quipped that he was not permitted to have 12 players on the pitch at once.

[17] July 2004 saw Chapman depart Fulham to sign for Charlton,[17] making her debut in a 1–0 Community Shield win over Arsenal at Broadhall Way.

[20] She then missed the conclusion of the 2004–05 season, including Charlton's FA Women's Cup win, with a broken hand sustained on international duty.

She was praised by manager Laura Harvey after scoring late, decisive goals against Rayo Vallecano Femenino and Linköpings FC which helped to take Arsenal through to a UEFA Women's Champions League semi-final against eventual winners Lyon.

[32] In May 2011, following injuries to Faye White and Jayne Ludlow, Chapman captained the Arsenal team which beat Bristol Academy 2–0 at the Ricoh Arena to reclaim the FA Women's Cup.

[37] In August 2015 Chapman captained Chelsea in their FA Women's Cup final against Notts County, the first time the event had been staged at Wembley Stadium.

[40] In October 2015 she played in Chelsea's 4–0 win over Sunderland which secured the club's first FA WSL title and a League and Cup "double".

[41] At the 2018 FA Women's Cup Final, Chapman secured a record 10th winner's medal as Chelsea beat Arsenal 3–1 at Wembley.

[5] Chapman made her senior debut for England at 17, during the 2001 UEFA Women's Championship qualification tournament, replacing Samantha Britton after 73 minutes of a 1–0 win over Switzerland in Bristol on 6 May 2000.

[49] Without Chapman – pregnant with her first child – England eventually failed to reach the 2003 FIFA Women's World Cup after a play-off defeat to France.

[50] Despite a hand injury, Chapman also played every minute of all three games[51] for England at the 2005 UEFA Women's Championship, now featuring in midfield as she did at club level.

[52] At the 2007 FIFA Women's World Cup Chapman started three matches, missing the group game against Argentina after picking up her second booking of the tournament during an impressive performance against Germany.

[57] Ahead of a March 2011 friendly against United States, Chapman unexpectedly withdrew from the England squad and quit international football.

[60][61] At the 2011 World Cup, Powell stressed that the FA had tried hard to accommodate Chapman's requirements: "Katie was away with us in 2009 when we paid for her family to come along but at the end of the day there is not a bottomless pit of money in the women's game.

Chapman recalled that she asked for time off to look after her children in a brief conversation with Powell, only to receive an e-mail cancelling her central contract three hours later.

[63] Powell's successor Mark Sampson eventually recalled Champman to the national team squad in February 2015, for a friendly against the United States in Milton Keynes.

[67] England eventually finished in third place after Chapman, starting her fifth match of the tournament, helped them beat Germany 1–0 in the bronze medal play-off.