He has played for Calvisano from 2000 to 2014. Paul Griffen was raised in New Zealand and played his early rugby at Blaketown Reconstruction Finance Corporation and at Linwood Reconstruction Finance Corporation later representing the West Coast in 1993 and Canterbury in 1997 in the National Provincial Championship. In 1999 he left New Zealand and joined Partenope of Naples, a second tier Italian side where he played for one season.
Griffen transferred to Calvisano for the start of the 2000-2001 season appearing in the Super 10.
He has now spent over ten seasons at Calvisano
In 2004 he was selected by coach John Kirwan to represent Italy against England in the 2004 Six Nations Championship. He was replaced as first choice scrum-half by Alessandro Troncon for the 2005 Six Nations Championship appearing as a replacement on two occasions.
The highlight of Griffen"s career was his selection by Italy coach Pierre Berbizier for the 2007 Rugby World Cup where he appeared in three games. Griffen was omitted from the national team for the 2008 Six Nations Championship but was recalled after a sixteen-month absence by the new Italy coach Nick Mallett for the 2009 Six Nations Championship where he made four appearances.