Kemp reunites with Pulis at Palace
Former Palace player Kemp worked alongside Pulis at Stoke, Portsmouth and Plymouth and the pair have been reunited at Selhurst Park.
"We've worked together for many years and have the same philosophy on tactics and work ethic."
Kemp will join Pulis on the bench at Tottenham on Saturday.
Meanwhile, Palace winger Jimmy Kebe has joined Leeds on loan until the end of the season.
McDermott actually scouted Kebe at Reading and later worked with him as a manager, winning promotion to the Premier League in 2012.
"Jimmy is a player that I scouted from France in 2006. He has fantastic pace, he is a real team player, and he made and scored goals for us in the Championship and the Premier League. I'm delighted he's come on board and I'm really looking forward to working with him again," McDermott said.
Kebe joined Palace in the summer but has failed to make an impact and has been restricted to six appearances this season.