Between 1984 and 1992 Matthews made 38 full senior appearances for Ireland. On 10 November 1984 he made his senior international debut against Australia at Lansdowne Road. He was a member of the Ireland team that won the 1985 Five Nations Championship and the Triple Crown. He subsequently represented Ireland at the 1987 Rugby World Cup. On 29 October 1988 he captained Ireland for the first time against Western Samoa. He captained Ireland on 13 occasions, including at the 1991 Rugby World Cup when Ireland came extremely close to defeating eventual winners Australia in the quarter-final. He won his 38th and final cap on 2 February 1992 against Scotland at Lansdowne Road.[2][1][10][11] Matthews international career has been commemorated on at least two postage stamps. He was the eighth Ireland rugby union international to appear on a stamp. Along with Steve Smith he was depicted on two stamps in a set of nine issued by Tajikistan for the 1991 Rugby World Cup. In his stamp he is seen tackling Australia's Michael Lynagh. He was also featured on one of the nine rugby union stamps issued by the Republic of Turkmenistan during 2000. Again he is playing against Australia at the 1991 Rugby World Cup.[12]
Between 1994 and 2015 Matthews served as a rugby union co-commentator with BBC Sport. He was encouraged to become a co-commentator by Jim Neilly. He has also worked for TV3, including at the 2007 Rugby World Cup.[3][7][25][26] Away from rugby union, Matthews spent twenty years working in the pharmaceutical and consulting industries where he held various roles in sales, marketing, human resources and general management.[3][4]