Johnston was subsequently named captain of Ireland, and was a regular fixture in the national team until his retirement in 2013.

Johnston made his first-class debut for New South Wales in a Sheffield Shield match against Tasmania in March 1999.

[4] Johnston first played club cricket in Ireland in 1995 and returned for four more seasons, meeting his former wife Vanessa, with whom he had two children.

Johnston was in the Irish squad[10] and they reached the final, losing to Scotland, but still qualifying for the 2007 World Cup.

[13] The following year started with several matches against English county sides[2] before captaining Ireland[14] in their first ever One Day International against England.

In October 2007, he published a book "Raiders of the Caribbean" (co-authored with Gerard Siggins) with The O'Brien Press which tells the story of Ireland's performances in the 2007 Cricket World Cup.

Johnston explained the rest was to allow him to focus on his family life, his professional career, and allow his body to recover from various injuries.

[29] Cricket Ireland announced their first central contracts for players in June 2009; previously the Ireland team had been made up of amateurs, aside from those players who could forge careers in the England Cricket Board's County Championship, and this was part of an initiative to make the sport more professional.

[30] Johnston won his 100th cap in the August 2009 ODI loss to England, when he was named Man of the Match, for 20 not out and bowling figures of 10–2–26–4.

He resigned as coach in October 2022, after a tabloid newspaper published details of alleged extramarital affairs that occurred while he was on tour with the team.