The musician, above, has joined the campaign over Bearsden Primary, which is facing the axe by East Dunbartonshire Council.
Mr Knopfler, a former pupil, said the school on its current site at Bearsden Cross "plays a vital part in community life".
Mr Knopfler, whose hits include Brothers In Arms, Sultans Of Swing and the theme music for the film Local Hero, said: "I was dismayed to hear Bearsden Primary is under threat of closure.
"I was very happy there. The school is ideally situated and I used to enjoy walking there and back every day.
"It sits in the heart of the catchment area and there is no doubt it plays a vital part in community life."
As previously reported in the Evening Times, Bearsden Primary is one of 24 schools in the council area under threat from a total of 36.
On December 10, councillors voted 14-10 to go out to public consultation on a set of proposals for school closures and mergers.
Campaigners claim council plans ignore Bearsden's record for educational attainment and its high school roll, which are both above the local authority average.
Another former pupil and pop star, Darius, is also backing the campaign and has posted his support on Twitter, the online social networking site.
Wendy McLaren, a spokeswoman for the action group Save Bearsden Primary, said the high-profile support from former pupils shows how well thought of Bearsden Primary is.
Mrs McLaren, who has two children at the school, said: "We believe shutting the school will have a negative impact on our whole community.
"It will have implications for local businesses, increased traffic congestion and also stop our children from gaining the health and educational benefits of being able to walk to their local school in the heart of their community and catchment."
Council plans would see Bearsden Primary moved to and merged with Castlehill Primary on its site, which is a mile and a half away.
There is no option to retain and refurbish Bearsden Primary on its current site.