Crown post offices in Scotland were closed on Monday while others operated with a skeleton staff during a strike over jobs, pay and closures.
Hundreds of members of the Communication Workers Union (CWU) took the industrial action in places including Edinburgh, Aberdeen and Dunfermline.
It follows a UK-wide stoppage on Saturday and comes before a strike by workers in England, Wales and Northern Ireland on Tuesday.
Larger offices in Scotland were kept going by management while smaller ones were closed, according to CWU area rep David McCloy.
"This is the 11th day of action since the end of March and the staff are very supportive," he said. "It's not just about the jobs and pay, it's about the whole issue of keeping post offices alive."
The strikes were staggered around the August bank holiday in England, Wales and Northern Ireland.
Some Scottish offices which follow the same holiday pattern will be hit by industrial action on Tuesday. They include Perth and Dundee, Mr McCloy said.
The dispute, involving 4,000 staff across the UK, is over plans to franchise or close more than 70 Crown post offices - the larger high street branches owned by Post Office Ltd. The strike action is the 11th round since March and the CWU says there are no signs of it stopping unless an agreement can be reached.
Kevin Gilliland, network and sales director at the Post Office, said: "We are extremely disappointed at the CWU's decision to call further strike action. 'This action can only cause disruption to customers, cost our people money and place further pressure on the Crown network which is currently losing £37 million a year.
''We must continue with our plans to turn around the Crown network to ensure we keep these branches on high streets and in city centres across the UK. We remain open to discussions with the CWU on pay options which do not add to the current loss of public money."