A regional court in the southwestern town of Weinheim heard the doctor was convicted of “issuing incorrect health certificates” to people from across Germany, most of whom she had never met on Monday.
During the trial the defendant argued wearing masks was harmful to people’s health.
In addition to the prison sentence she was handed a three-year work ban and ordered to pay 28,000 euros, the sum she had received for issuing the medical certificates. Her office assistant was fined 2,700 euros.
The doctor’s lawyer intends to appeal the verdict, public broadcaster SWR reported.
Dozens of supporters gathered outside the court in Weinheim, north of Heidelberg, to protest against the verdict and Germany’s pandemic restrictions.
Germany ended requirements to wear masks in many indoor settings last year, though they are still compulsory on long-distance trains, in doctors’ practices, hospitals, nursing homes and on some regional public transport.
The trial came as UK health chiefs pleaded with the public to avoid get ill unnecessarily as the NHS faces “major crisis”.
The viruses sweeping the country are putting added pressure on the NHS at a time when the service is already extremely stretched.
NHS Confederation Chief Executive Matthew Taylor, which represents organisations in the health service, said the situation facing hospitals was “very difficult”.
“There’s no doubt the situation is very difficult - that’s why many trusts have declared critical incidents,” he told the BBC on Tuesday.