Doors will remain open at pharmacies in the Helsinki area, but the protest action will shorten opening hours.
The move follows a lack of progress in talks aimed at securing a new deal on pay and conditions.
A fresh round of negotiations between the Union of Pharmacists and employers is to take place next Sunday.
Pharmacists are seeking, on average, a 500 euro pay increase over a period of two years. If Sunday's talks fail to secure an agreement, pharmacies in many cities across Finland will go on strike to be followed by nationwide action.
YLE