In 2003, he was appointed as coach of the newly formed Llanelli Scarlets regional side, guiding them to the Celtic League title in their first season.
Jenkins finally took over as Wales coach when Ruddock resigned during the 2006 Six Nations, but his tenure was unsuccessful, winning just six of his 20 games in charge.
Older than teammate Ray Gravell by a day, he was the second-youngest member of the Llanelli team that famously beat New Zealand 9–3 at Stradey Park in 1972.
[31] Jenkins' first duty as Wales coach was a two-test tour of Argentina in June 2006, for which he picked an inexperienced squad with an average age of 24.
On that tour, he gave an international debut to lock Alun Wyn Jones,[33] who went on to become the most-capped player in rugby history.
[34] After returning from Argentina, delayed by a lost passport,[35] Jenkins' first home test match saw a creditable 29–29 draw with Australia to start the 2006 Autumn internationals,[36] followed by comfortable wins over the Pacific Islanders[37] and Canada,[38] before a 45–10 loss to New Zealand.
[39] In the 2007 Six Nations, Wales lost four of their five matches, including a 23–20 defeat against Italy;[40] after that match, Jenkins criticised the officials for miscommunicating the amount of time left in the game as Wales spurned an opportunity to kick a penalty that would have tied the scores, instead opting to kick to touch in search of a game-winning try.
[50] A 72–18 win over Japan five days later set up a decisive match against Fiji on 29 September, with the winner qualifying for the quarter-finals as runners-up of Pool B.
[52][53] After the match, Jenkins spoke of his desire to continue coaching Wales, at least until the expiry of his contract after the 2008 Six Nations;[54] however, Jenkins was sacked the following day, on 30 September 2007, informed of the WRU's decision by chief executive Roger Lewis and chairman David Pickering at the team's hotel car park.
[61] Jenkins spent a week working at London Welsh RFC in February 2008, but would not commit to any interest in a permanent role at the club.
[62] Following the sacking of Phil Davies as Scarlets coach at the end of the 2007–08 season, Jenkins was thought to be a leading contender to resume the role,[63] but while chief executive Stuart Gallacher said Jenkins could return to the Scarlets, it would not be in a coaching capacity;[64] the role ultimately went to Nigel Davies.