Shoppers can park for free in council-owned car parks in town after 2pm on Saturday 9, 16 and 23 December.
The campaign has been launched to encourage shoppers to visit their local High Street over the festive period.
SKDC Cabinet Member for Retail and Visitor Economy, Cllr Nick Robins, said he wants people to keep it local this Christmas and support Grantham's town centre shops and businesses.
"South Kesteven already has some of the lowest car park charges in the area, but by offering free parking across council-owned car parks during the run up to Christmas we hope to deliver a real boost to the town centre," he said.
"The aim is to encourage shoppers and visitors from outside our district to stay longer in town where there is a lot to enjoy, from independent shops for those special gifts, to well known high street names and a selection of fine restaurants and cafes."
Shoppers will not have to pay and display a ticket during this special offer period. Signs will be displayed in car parks and on the car parking machines, explaining the times when the offer is valid (after 2pm each Saturday in December).
Disabled people can continue to park free at all times in designated bays when they display their 'blue badge'.