[1][2] On 16 August 1979 he switched codes signing for St. Helens rugby league club for a world record £27,000 (based on increases in average earnings, this would be approximately £183,200 in 2015),[5] and making his début in the 28–16 defeat by Widnes in the first round of the 1979 Lancashire Cup at Knowsley Road, Eccleston, St Helens on Sunday 19 August 1979.
[6] In September 1986, he returned to St. Helens to take up the position of fitness conditioner and a move into coaching the Wales national rugby league team led to some very creditable performances under his guidance including a World Cup semi-final match against the eventual winners Australia with a first half performance that gave Wales a half time lead.
Whilst playing for Llanelli Griffiths took up his first senior coaching appointment in 1977 at the age of 25 for Newcastle Emlyn RFC.
Griffiths was appointed to the Wales Squad Coaching team on 1 July 2001 by Graham Henry and remained a part of the set up through the 2003 Rugby World Cup and five Six Nations campaigns, including the 2005 RBS Six Nations Grand Slam where he was credited for his part in tightening Wales' defensive line, particularly in their tackling performance against England.
Clive Griffiths joined Worcester Warriors as Head Coach and assistant to Director of Rugby Mike Ruddock in June 2007 on an initial two-year deal.