The Verdi union is negotiating on behalf of around 2.5 million employees in the public sector, including in public transport and at airports.
Railway and transport union EVG negotiates for around 230,000 employees at Deutsche Bahn (DBN.UL) and bus companies.
Verdi has called on around 120,000 employees in the transport and infrastructure sectors, including ground and air traffic service providers, shipping, motorways and municipal ports, to join the strikes.
We want a negotiable offer," said Martin Burkert, the chairman of the EVG union, which represents workers at 50 transport companies, including railway operator Deutsche Bahn.
German airport association ADV also condemned the strikes expected to hit around 380,000 air travellers on Monday as all airports across Germany, except Berlin, would come to a virtual standstill.