Anne McTaggart, who is currently a Glasgow city councillor for Anniesland and Drumchapel, confirmed her switch on Friday.
It brings the total number of SNP councillors in Glasgow to 38, with Labour reduced to 30.
Ms McTaggart was first elected as a councillor in a by-election for the ward in 2009, before becoming a list Labour MSP for the Glasgow region in the 2011 election for the Scottish Parliament.
She said: "I really want to be part of something positive. Labour hasn't done anything positive of note for a long time in Glasgow.
"Meanwhile, I've watched the SNP delivering positive policies, at a national and a city level, which are the right ones for my community."
First Minister Nicola Sturgeon tweeted: "Great to welcome former Labour MSP @AnneMcTaggart23 to @theSNP and our Glasgow council group."
Susan Aitken, leader of Glasgow City Council, told the Evening Times: "Anne's decision is an exceptionally brave one. It cannot have been easy.
"But the journey which Anne has made is one which many people across Scotland have been making over the past decade, and particularly since 2014.
"She is part of a growing movement which sees that an independent Scotland is not only the best option for the future wellbeing our communities and our citizens, it is the only way to protect them from the chaos of Brexit and a broken Westminster system."