Holt has been a member of the Town backline since 2006 when he arrived from Wrexham on a free transfer. He has made 220 appearances for the Cobblers in all competitions and also found the net 17 times in his career at Sixfields.
Holt and Hall are the latest of Town's squad to not have their contracts renewed, with Lewis Young, Nat Webberburn, Michael Built, Jason Crowe and Ryan Gilligan also set to depart in the summer.
Speaking on Holt, Town boss Aidy Boothroyd said: "It is always difficult to see a player leave who has done so well for the club over many years. It is even harder when they are as a good a character as Andy is but things move on and decisions have to be made
Hall, meanwhile, made just three appearances for since his arrival last summer, and Boothroyd added: "Freddy also goes with our thanks and best wishes and we hope that he too can get himself fixed up elsewhere. Again, by telling the lads early we are hopefully giving them a headstart in their search."