Picket lines formed outside university buildings in Edinburgh, Glasgow, Aberdeen and Dundee in protest at a 1% pay offer for lecturers and administrative workers.
The University and College Union (UCU) said employees had faced a "real-terms pay cut" of 13% since 2008.
Mary Senior, UCU's Scottish official, said there had been a good turnout at the picket line at Queen Margaret University in Edinburgh.
She said: "We're very upbeat, we've been explaining to people why we are out today and people have been signing our petition.
"Lectures have been cancelled and the library in Glasgow is closed, so the action is having an effect. We want the employers to come back to the negotiating table and make a better offer."
Unison and Unite members were also taking part in yesterday's strike, said to be the first walk-out over pay at universities in seven years.
Pickets were taking place outside Old College, Edinburgh University and at Glasgow University's main gate on University Avenue.
Protests were also organised at Stirling, Aberdeen, St Andrews and Dundee.
Ms Senior said: "This year's miserly 1% pay offer, at a time of rising bills and increased pension contributions, was the straw that broke the camel's back.
"Staff love their jobs, but their goodwill cannot continue to be taken for granted."
Large groups of striking staff gathered at the gates of Glasgow University, holding placards and cheering when passing motorists sounded their horns in support.
Bill Stewart, 61, a senior teacher in civil engineering, said: "Our argument is that there's money in the system to give us a better pay rise than 1%, because that would be yet another cut in terms of the inflation rate currently.
"We are simply trying to persuade the employers to come back to the negotiating table."
Marc Livingstone, who works in admissions, said lecturers, cleaners, janitors and administrative staff were all taking part in the walk-out.
The 31-year-old said: "We've been expected to do more with less resources and stress levels are increasing.
"I think it would be good if we got some money to recognise our hard work."
Maths and English student Eilidh Ruthven, 17, said she was advised that a maths class would not be taking place because of striking cleaning staff.
The UCEA, the body that negotiates wages for university workers across the UK, said that on top of the 1% general pay rise, many university staff get other contributions that will increase pay by 3% overall.
A spokesman said: "Institutions tell us that the vast majority of staff understand the reality of the current financial situation and do not support action which would harm their institutions, and especially their students."
A spokesman for Glasgow University said: "With the exception of the library and the Hunterian Museum, which were closed because of today's industrial action, the university was otherwise open as normal with only minimal disruption to some classes."