A goalkeeper, he played for Leeds United A.F.C., Scunthorpe United F.C., Chesterfield F.C. and Swansea City A.F.C.. Despite regularly being called up to the Wales squad as cover for Dai Davies, Letheren never achieved a full international cap. He was also a successful cricketer in the South Wales Cricket Association, playing mainly for Dafen Welfare CC, as a medium pace bowler and middle order batsman.
His son Kyle Letheren plays professional football, as a goalkeeper.