Former party leader Iain Gray is among those who have today announced their backing for the Glasgow MSP, along with Mary Fee, chair of the Scottish Parliamentary Labour group and Ian Murray who chairs the party's MPs group at Westminster. MEP Catherine Stihler has also given her endorsement.
His opponent for the leadership, Richard Leonard, already appears to have secured the Corbynista support base, with the Campaign for Socialism and key Corbyn ally, the MSP Neil Findlay, backing the former trade union official.
Mr Sarwar said: “I am humbled to have received support from so many colleagues in such a short space of time.
“Labour is revitalised in Scotland and we need a united party in Holyrood that is fighting the SNP and ready to form Scotland’s next government.
“And we need a united Labour Party working together across the UK to elect Jeremy Corbyn as Prime Minister.
“During this leadership election, with the help of my colleagues, I will be setting out a positive vision for our country that puts Labour values at the heart of Scotland's future.”
There are 32 Scottish Labour parliamentarians, including 23 MSPs, meaning Mr Sarwar already has the backing of almost half.
Others who declared their support for Mr Sarwar today include MSPs Mark Griffin, James Kelly, Lewis Macdonald, Colin Smyth and David Stewart.
The party's economy spokeswoman Jackie Baillie, Daniel Johnson, Pauline McNeill and Neil Bibby and MP Martin Whitefield had already declared their support for Mr Sarwar .