He will become the new manager in July and has agreed a one year contract with the option of a further twelve months.
Penrith born Grainger, 32, has spent the last five seasons with Carlisle United but, prior to that, plied his trade north of the border serving the likes of Brechin City, Dundee United, St. Johnstone, Hearts and St Mirren after starting his career with Gretna.
The left back is coming to manage the club primarily but will register as a player and may add to his near 400 league appearances in Evo-Stik West should that be necessary.
He obtained his UEFA A License two years ago and has coached in the Carlisle United Academy and runs the self owned Cumbria Football Academy, welcoming the fact that Reds are now establishing their own pathway to first team football under Brian Dawson.
Danny, who watched Workington play a couple of times before the end of the season, can draw on an illustrious playing career which has included numerous promotions and Cup Final appearances in Scotland and several player-of-the-year accolades during his time at Brunton Park.
Danny (second left) on duty for Carlisle United in pre-season at Borough Park.
So, after seventeen seasons in the professional game, Danny will bring all that experience to Workington and is looking forward to his first stint in management.
He will name his backroom team in due course.