Negotiations have been going on for two weeks with no visible progress.
The 9,300-member Finnish Pharmacists' Association is prepared for a long strike. The union is seeking pay wages averaging 500 euros a month over the next two to three years.
The strike expanded on Monday to include about 150 more pharmacies. It now affects nearly 60 percent of the country's pharmacies.
"Compared to other fields or other professionals in the private sector, our monthly salaries are 500 or even 900 euros lower than others," says Inka Puumalainen, president of the Pharmacists' Association.
"We feel that ours is a demanding, expert job. But the salary has not met this expectation," she adds.
A list of pharmacies affected by the strike can be found in PDF format in Finnish on the Finnish Pharmacists' Association website.