In 2004, Jeffers joined Charlton Athletic, where he spent two seasons, including spending time on loan at Scottish club Rangers.

He left Everton in May 2021 to join Ipswich Town as a first-team coach, a role he held until December.

In September 2022 he joined National League side Oldham Athletic as first-team coach with additional responsibility for overseeing the introduction of the club's new B-team.

[2] Jeffers began his career at Everton, making his first-team debut as a half-time substitute for Dave Watson on 26 December 1997 at Old Trafford at the age of 16 years.

[11] Arsenal won the FA Cup in 2002 and 2003 but Jeffers was left out of both match day squads, the latter due to injury.

[20] He only scored twice (with both goals coming against Fulham in the FA Cup; once in the original tie[21] and again in the replay)[22] in 22 appearances for his team, before falling out with manager David Moyes and prematurely returning to London.

[23] He signed for Arsenal's Premier League rivals Charlton Athletic on 10 August 2004 on a two-year contract for a £2.6 million fee.

[25] He joined Rangers on loan on 31 August 2005 for six months but returned in December after his performances in the Scottish Premier League failed to live up to expectations.

[7] After a lively start against Stoke City on 20 October 2007, Jeffers was on the end of a tackle from Ryan Shawcross and was stretchered off with ankle ligament damage.

[37] Jeffers came back as a substitute on 10 December 2007 versus Hull City, but ended up on the losing team after a 1–0 loss.

[38] In the summer of 2008, Jeffers had more problems with his ankle and also picked up a groin injury, leaving him injured until September 2008.

[7] He returned to first-team action with a 25-minute substitute appearance in a 6–0 defeat at Reading in mid September 2008 and then a further ten minutes against his former club Ipswich Town.

[39] Jeffers scored his third goal for the Wednesday on 17 January 2009 in a 4–1 win over Charlton at Hillsborough, but was sent off in the next match against Nottingham Forest for a foul on Joe Heath.

[40][41] On 25 August 2009, Jeffers was sent off for headbutting Port Vale player Tommy Fraser during the 2–0 League Cup defeat.

Manager Brian Laws considered his behaviour unacceptable, fined the player the maximum permissible amount and placed him on the transfer list.

[51][52] He made his debut coming on as a second-half substitute for John Sutton in the 6–0 defeat to former club Rangers.

[63] He was released by Accrington at the end of the season, and had trials with Bury,[64] Brunei DPMM of the S.League,[65] and Chester,[64] but none chose to sign him.

[72] Jeffers has one cap for the England national team, scoring a consolation goal in a defeat by Australia in a friendly on 12 February 2003.

[73] Unable to find a new club after his playing contract with Accrington Stanley had expired, Jeffers began working for Everton's academy on a voluntary basis in 2014.

He was also part of Duncan Ferguson's back room staff during his spell as caretaker manager of Everton in 2019.