The Scots Tory leader was present at the Home Secretary's formal campaign launch today, after announcing her endorsement at the weekend for him to replace Theresa May.
The First Minister said Mr Javid's readiness to accept No Deal Brexit was a concern and compared with Ms Davidson's trenchant support for Remain during a keynote campaign event during the 2016 referendum at Wembley.
Ruth Davidson is supporting a candidate who says he favours a catastrophic no deal Brexit over no Brexit at all," Ms Sturgeon said on Twitter.
What a turn around from the great Remainer of Wembley stadium.
"And hard to imagine a position more out of touch with the vast majority in Scotland."
The Scottish Conservatives have said the party has "strengthened devolution" and handed new powers to the Scottish Parliament.
“Unfortunately, due to the total incompetence of Nicola Sturgeon’s government, those powers have either been mishandled or delayed because the SNP doesn’t know what to do with them."
Mr Javid launched his Tory leadership campaign video on Tuesday with a focus on his heritage and business background.
The Home Secretary, 49, pledged to "deliver Brexit" and convince voters to take a "fresh look" at the Conservative Party.
Beginning in his family home, where he lives with his wife and four children, Mr Javid then travels to Bristol, where he moved as a child after he was born in Rochdale.
He tells viewers about his father, who moved to Britain from Pakistan in 1961 and became a bus driver, and visits the family shop where he grew up.
"I wanted to give back to the country that's given me so many opportunities," says Mr Javid, who also introduced his dog in the two-minute clip.
"I feel really privileged to have been given the experience and responsibilities in government that I've had.
"These are incredibly challenging times. The country feels very divided.
"We need leadership. We need someone who can help heal the country and bring people together."