Jackman represented Ireland at U19, U21 and college levels and captained Ireland A before graduating to the senior Ireland team. He was included in the squad for the 1998 tour of South Africa but was not capped. He was capped twice during the 2005 tour of Japan and won two further caps during the 2007 tour of Argentina. He was also included in Ireland's 2008 Six Nations Championship squad and featured in all five games.
