About 4,000 demonstrators have turned out to march through Oxford, according to police, twice as many as organisers expected.
More than two-thirds of Oxfordshire's schools were shut or partially closed and other public services were hit.
President of Oxfordshire and District TUC Gawain Little said the issue of increasing pension contributions was a "serious concern to everybody".
Henley Conservative MP John Howell said the government had to make savings.
Mr Howell called on the strikers to continue talks and added: "This is something that we need to do as a country in order to get out of the mess we are in.
"The government has been prepared to listen and changes have been made."
'Work until 68'
Unions had told the BBC they expected the march from the city centre to be the biggest in the South East outside London.
A number of feeder marches congregated at the Plain in the city at about 14:00 GMT, moving to Broad Street for a rally at 15:00 GMT.
Andrew Morgan, a CPS prosecutor from Oxford on the march, said: "We're angry the government is tearing up the 2007 pensions agreement it had with the civil service."
Coaches brought people into the city from other parts of Oxfordshire including Banbury, Abingdon and Witney.
Oxfordshire County Council said 209 of its 291 schools were closed or partially shut.
Ed Finch, a striking teacher, said: "Every parent and child I have spoken to about the arguments have said 'fair enough, you do it'."
Ian McKendrick, a staff nurse on the picket line outside Warneford Hospital in Oxford, said: "I'm looking at a future ending up on benefits because I work in acute admissions and I can't do that job at 66."
Richard, 66, from Oxford, who did not want to give his full name, said he still works and that he would "sack anyone who is on strike".
"The strike is pointless," he said. "Anyone who doesn't want to support the British economy should be sent to Greece.
"I have put money into my own pension pot from my own funds, I've never had any contributions to it.
"I'm totally and utterly fed up with people who want to hold the country to ransom."
Lecturers and support workers at Oxford Brookes University were among those on strike but most Oxford University staff did not take action.
Hospitals, bin collections, job centres and libraries have also been affected across the county.
NHS doctors and midwives were not striking and the council's fire and rescue service was unaffected.
The courts were open as normal.