[5] He became a regular member of the Watford side that won promotion to the First Division and finished runners-up in the league in the 1982–83 season under manager Graham Taylor.

[8] Jackett made his international debut for Wales, for whom he was eligible through his Welsh-born father, on 22 September 1982 in a 1–0 win over Norway in a Euro 84 qualifier.

[9] Upon his playing retirement, Jackett remained at Vicarage Road and, having already undertaken many qualifications, became a member of the club's coaching staff.

[3] In February 1996 he and fellow long-term Watford player Luther Blissett were selected by the returning Graham Taylor to run the first team, while he served as general manager.

When Taylor left Watford at the end of the 2000–01 Division One season, Jackett was released on the instruction of incoming manager Gianluca Vialli.

[11] Following his exit from Watford he joined Ian Holloway at Queens Park Rangers as assistant manager and contributed towards their Division Two promotion campaign.

[12] After three years as an assistant, Jackett left QPR to replace Brian Flynn as manager of Third Division side Swansea City in April 2004.

[13] In his first full season in charge, the team were promoted from League Two, finishing in third place,[14] and also lifted the FAW Premier Cup in their last game at the Vetch Field.

[18] Jackett did however win silverware for a second consecutive season as the Swans won both the Football League Trophy,[19] as well as defending the FAW Premier Cup.

[24] Later in the year he was interviewed for the vacant managerial post at League One club Millwall after the sacking of Willie Donachie, but initially pulled out of the running.

Jackett once again led Millwall to Wembley in the 2012–13 season, when the team reached the semi-finals of the FA Cup where they lost to eventual winners Wigan Athletic.

[37] Jackett was again nominated for the Manager of the Month Award in October following an unbeaten run where his side earned 10 points from four games.

[38] Under his command, Wolves gained promotion back to the Championship at the first attempt as League One champions and set a new divisional points record of 103.

[51] On 31 March 2019, Jackett led Portsmouth to the EFL Trophy final, winning the tournament against Sunderland 5–4 on penalties after the game finished 2–2 in extra time.

[55] Shortly after the takeover of Gillingham by American businessman Brad Galinson in late 2022, Jackett was appointed director of football on 5 January 2023.