Jagielka started his career with Sheffield United, joining current team, Everton, in 2007 for a fee of £4m. He is a former England under-21 international, being capped six times and scored 2 goals for the team. He has also gained recognition with the England B team, appearing once for them. Jagielka has been called up by England manager Fabio Capello in his provisional squad for the games against Trinidad and Tobago and United States, where he came on as a substitute in the second half against Trinidad and Tobago.
He established himself in the Sheffield United first-team in the 2002-03 season and started to attract the attention of other clubs, including Leeds United, who were linked with a £6m joint bid for Jagielka and United teammate Michael Brown, but Sheffield United said they would resist any attempts to sign the players.
Jagielka stated in April 2005 he was happy to stay at United, despite several Premier League clubs being interested in signing him. United manager Neil Warnock told West Ham United in June 2005 that Jagielka would not be sold, and in July Wigan Athletic made a £4m bid for Jagielka, after which United upped their valuation of him. By November, Jagielka had been linked with a £4m move to Bolton Wanderers, but United manager Neil Warnock said there had been no contact from Bolton.
Jagielka signed a new three-year deal with United in August 2006. Having recently played as team captain in Chris Morgan's absence, Jagielka gave United their first Premiership victory since April 1994 when he hit a 91st minute half-volley against Middlesbrough for a 2-1 win in September 2006. Despite being recognised as one of United's key players, chairman Kevin McCabe admitted that Jagielka could be sold if the price was high enough. In a home match against Arsenal on 30 December 2006, due to a thigh injury to starting goalkeeper Paddy Kenny and with his team 1-0 up, Jagielka was forced to play in goal for the remainder of the match. Arsenal were kept at bay for the remaining thirty-four minutes and Jagielka's late save from Robin van Persie secured the 1-0 victory. His ability to deputise in goal meant that Neil Warnock was able to, and usually did, do without a substitute goalkeeper on the bench.
By the end of the 2006-07 season, he had made 133 consecutive league appearances for United, including every league match in the 2004-05 and 2005-06 seasons and every minute of the 2006-07 season. When Sheffield United were relegated from the Premier League at the end of the 2006-07 season, Jagielka was linked with moves away from United and goalkeeper Paddy Kenny said he believed it was time Jagielka moved on. New United boss Bryan Robson urged Jagielka to wait for the outcome of the clubs relegation arbitration hearing before deciding to leave the club.
In July 2008, Phil was given the number 6 shirt for the following season which was previously worn by Mikel Arteta, as Mikel Arteta was given number 10.
Jagielka is a former member of the England under-21 team, and scored in a 2-0 victory over Slovakia at the Stadium of Light in June 2003.
On 10 May 2007, Jagielka was named in the England squad for the first time, to play a 'B' international against Albania. Starting on the bench, he replaced future Everton team mate, Phil Neville at right back at the beginning of the second half.
On 11 May 2008, Jagielka was named in the senior England squad for the first time
for the friendlies with United States and Trinidad and Tobago. He subsequently expressed his delight at the call up
and publicly thanked everyone at Everton for their help.
On 1 June 2008, Jagielka got his first international cap for the senior team against Trinidad and Tobago after being brought on as a substitute
He was named the Sheffield United Supporters Club Player of the Year for the third successive year in April 2007 and won the Capital One Player of the Year in May 2006.
He has also been named the inaugural Championship Player of the Year for the 2005-06 season. He was also named in the 2006 PFA Championship Team of the Year.
When promotion to the Premiership was confirmed on Saturday, 15 April, 2006, it was a double celebration for the Jagielka family with older brother Stephen Jagielka celebrating promotion to the Football League with Accrington Stanley. Steve currently plays for AFC Telford United.