Their union, Adedy, called for the stoppage in a statement issued today, saying it was to show their opposition to the outline agreement with the eurozone.
It will also urge the civil servants to take part in a demonstration against the reforms scheduled to take place in front of parliament late Wednesday.
This will be the first strike to happen under the six-month-old government of Prime Minister Alexis Tsipras, who is head of the radical left coalition Syriza.
Demonstrations were already to take place in Athens late Monday against the latest reform package, which requires parliament to back tax hikes and pension cuts in return for the eurozone bailout worth up to 86 billion euros ($96 billion), and against the euro. Without the loan, Greece's economy is likely to shatter, with exit from the euro a very real possibility.
To secure the rescue, Tsipras is going to have to win parliamentary backing, maybe relying on opposition votes if many of his Syriza MPs rebel.