Coughlan started playing rugby with Old Christians at the age of 10. He continued playing when he went to CBC, and was selected for Irish Schools. He went to UCC, and played for Irish Universities. He joined Dolphin in 2001 and has played 85 times for them in AIB League/Cup, scoring 32 tries, a club record. Coughlan also played on the Irish Sevens team in 2008 that qualified for the 2009 Rugby Sevens World Cup, which was held in Dubai.
Munster
Coughlan made his Munster debut against Cardiff Blues in the Celtic League in September 2006, and his performances in his first season earned him a full contract. He made one appearance for Munster during their victorious 2007–08 Heineken Cup campaign. Coughlan was one of the stars for Munster in their 16–18 defeat by New Zealandat the opening of Thomond Park in November 2008. Denis Leamy's injuries propelled Coughlan into the Munster starting XV in the 2009/2010 season, and since then he has become a mainstay in the team. Coughlan captained Munster during their historic 15–6 win over Australia in November 2010, and he won the Munster Player of the Year award for 2011, beating fellow nominees Keith Earls, Ronan O'Gara and Doug Howlett. He started at Number 8 for Munster as they beat old rivals Leinster 19–9 to win the 2011 Magners League Grand Final. Coughlan was ruled out of the remainder of the 2011–12 season after a fractured bone in his hand, sustained in Munster's Heineken Cup quarter-final defeat against Ulster on 8 April 2012, required surgery. In January 2013, Coughlan agreed a contract extension with Munster. Coughlan scored a try and won the Man-of-the-Match award in Munster's 2013–14 Heineken Cup Round 6 38-6 win against Edinburgh on 19 January 2014, a win that secured a home quarter-final for Munster. Coughlan was nominated for the IRUPA Unsung Hero 2014 award on 23 April 2014. Coughlan was also nominated for the Munster Rugby Senior Player of the Year 2014 award on 1 May 2014. He won the IRUPA Unsung Hero 2014 award during the Annual Awards on 7 May 2014. On 27 May 2014, it was announced that Coughlan would be leaving Munster in June 2014.
Coughlan was called into the senior Ireland squad for the 2012 Six Nations Championship to replace the injured Leo Cullen but did not play. He was also called up to the Ireland squad for the uncapped warm-up against the Barbarians on 29 May 2012 in Gloucester. He came on in the 60th minute for Chris Henry. He was called into Ireland's training squad for the 2013 Six Nations Championship on 21 January 2013. Coughlan captained Ireland Wolfhounds in their friendly against England Saxons on 25 January 2013. He was added to Ireland's squad for their game against Scotland on 17 February 2013. On 23 October 2013, Coughlan was named in the Ireland squad for the 2013 Autumn Tests.
Retirement
On 28 April 2017, Coughlan announced that he was retiring from rugby union upon the conclusion of the 2016–17 season, bringing to an end his 11-year professional career in which he won 137 caps for Munster, 69 for Pau and 1 for Ireland Wolfhounds.
