Irfan Rabbani will join the SNP opposition group on the council, which Labour controls with a majority of 15.
The 49-year-old said he would not be standing in the local elections in May although he would be campaigning for other SNP candidates.
Mr Rabbani has represented Glasgow's Pollokshields ward since 2007. He had been a Labour member for 20 years.
A Labour councillor in Glasgow who had been de-selected by the party has defected to the SNP.