Debuchy started his senior career at Lille, where he won a Ligue 1 and Coupe de France double in the 2010–11 season.

[5] He began his career playing for his hometown club Union Sportive Fretin before joining Lille at the age of eight.

Debuchy was given the number 33 shirt and simultaneously made his professional debut and first start on 31 January 2004 in a league match against Metz.

In the final, Debuchy played the entire match as Lille defeated Paris Saint-Germain 1–0 at the Stade de France.

[20][21] The campaign was hugely successful for Debuchy on a personal level as he made his breakthrough in the French squad as well as being named in the UNFP Team of the Year.

[22] Following the season, Lille manager Rudi Garcia described Debuchy as a defender who "plays high and attacks but defensively is also very rigorous and he exudes confidence.

[23] Seven months after their failed bid, English club Newcastle United signed Debuchy on a five-and-a-half-year contract on 4 January 2013, for an undisclosed fee reportedly in the region of £5.5 million.

[28] On 1 January 2014, Debuchy was sent off for the first time in his Newcastle career after a rash challenge on Claudio Yacob in an eventual 1–0 defeat away to West Bromwich Albion.

[32] He made his competitive debut for Arsenal in their 3–0 victory over defending league champions Manchester City in the 2014 FA Community Shield at Wembley Stadium on 10 August 2014.

[33] Six days later he featured in the Premier League for the first time as an Arsenal player, his injury-time shot was saved and then converted by Aaron Ramsey for a 2–1 win at home against Crystal Palace.

[40] Debuchy made his return from injury on 18 April 2015, playing the full 120 minutes as Arsenal defeated Reading 2–1 in the FA Cup semi-finals at Wembley.

[41] He made no further appearances that season, with Héctor Bellerín instead playing at right-back in Arsenal's 4–0 win over Aston Villa in the Cup Final; Debuchy did not make the substitutes bench for that match.

On 27 November 2016, he made his first Premier League start against AFC Bournemouth at the Emirates Stadium, but went off with a hamstring injury after just 16 minutes as the Gunners won 3–1, ruling him out until January 2017.

[44] On 19 October 2017, Debuchy made his first start for Arsenal for almost a year against Red Star Belgrade in a 1–0 victory in the UEFA Europa League.

[45] On 24 October 2017, he played his first League Cup game of the season against Norwich City, which Arsenal won 2–1 after extra time.

[51][52] On 25 February, Debuchy scored Saint-Étienne's equaliser in the 90th minute of the Derby du Rhône against Lyon, an away Ligue 1 match which ended in a 1–1 draw.

[54] On 14 April, Debuchy scored in the 82nd minute from Saint-Étienne's only shot on target of the match, a Ligue 1 1–0 away win over Strasbourg.

[citation needed] Debuchy was named in Didier Deschamps' French squad for the 2014 FIFA World Cup in Brazil.