The LTA Tennis Foundation is funding the work with an investment of £61,326, delivered as part of its nationwide Parks Tennis Project to open up the sport to more people and bring public park courts back to life for the benefit of local communities.
The work is expected to be completed by early May with the courts managed by Grantham Tennis Club.
SKDC will also work with Grantham Tennis Club and the LTA to deliver a range of activities, including weekly free park tennis sessions for all ages, playing levels and experience, with racquets provided.
Local Tennis Leagues will provide friendly, sociable, opportunities to get active through local competition and new gate-access technology and booking systems will improve court accessibility for both Wyndham Park and Dysart Park courts.
Cllr Kelham Cooke, the Leader of South Kesteven District Council, said: "We are very grateful for such a significant investment. It's a great partnership for us with the LTA and Grantham Tennis Club and we look forward to seeing Wyndham Park's public tennis courts in better shape and back in full use.
"Both Wyndham Park and Dysart Park are holders of the prestigious Green Flag award, recognising the contribution they make to the community, and improved access to sports facilities will significantly enhance that contribution.
"Free tennis sessions for all ages and playing levels will also be incredibly valuable for people to improve their tennis or to take up the sport, and I am sure will be very popular."
Julie Porter, LTA Chief Operating Officer said:"We are delighted to be working with South Kesteven District Council to improve their park tennis facilities and provide more opportunities for anyone to pick up a racket and get active.
"This investment is part of the UK Government and LTA's Parks Tennis Project, and will mean that courts will be available for people to use for years to come. We will also be working closely with South Kesteven District Council to ensure that the local community have a range of accessible opportunities to get on court and open up our sport to many more people."
The LTA sees park tennis courts as vital opportunities for children and adults to get active, delivering significant physical and mental health and wellbeing benefits to participants.
Accessible facilities in parks are particularly critical to opening up the sport to those from lower socioeconomic backgrounds and women and girls.
Sarah Patton, for Grantham Tennis Club, said: "Grantham Tennis Club is very excited to be supporting SKDC and the LTA in providing more opportunities for the community of Grantham to play tennis, whatever 'tennis' is for them.
"We want to carry on our mission to show that the game is available and accessible to all and to see as many people as possible sharing in the enjoyment and benefit of being out in the fresh air, in lovely park surroundings and moving their bodies."
When work is complete, the courts and sessions will be available to book online via the LTA website https://www.lta.org.uk/play.