Coghlan was included in the training squad for the 2002 Women's Rugby World Cup before she made her Six Nations debut for Ireland on 2 February 2003 against . Coghlan subsequently represented Ireland at the 2006, 2010 and 2014 Women's Rugby World Cups. In 2008 she was first named Ireland captain, taking over the role permanently in 2010. During the 2009 Women's Six Nations Championship, she was a member first Ireland team to defeat . Coghlan captained the Ireland team that won the 2013 Women's Six Nations Championship. In 2013 Ireland also achieved both a Triple Crown and Grand Slam.