The Finnish Union of Practical Nurses (SuPer) and the Union of Health and Social Care Services (Tehy) imposed a ban on overtime and shift swaps early Wednesday morning. The unions say their members will refuse any such requests until Friday night.
The move comes in protest against government plans to weaken job security at firms with fewer than 20 employees.
SuPer and Tehy say there danger that the proposed legislation would allow firms to fire workers on flimsy pretences.
The Trade Union for the Public and Welfare Sectors (JHL) plans to begin its own overtime and shift-trading ban next Monday, 1 October.
All three labour groups demand that the cabinet rescind its proposal.
Bill would "intensify fear in working life"
"The lay-off bill proposed by the Finnish government intensifies fear in working life and doesn’t improve employment," said JHL President Päivi Niemi-Laine in a statement on Tuesday.
"More and more employers could plead lack of trust if employees raise concerns over workplace issues. The government has already made cuts to unemployment cover, parental allowances and the right to municipal day care. Now it wants to erode protection against dismissal," she charged.
The JHL estimates that its industrial action will cover nearly 100,000 members in the municipal and church sectors as well as in private social and healthcare.