The force received a call shortly before noon on Saturday about several ducks stranded in the middle of the dual carriageway, near Pratteln, cantonal police said on Monday.
Officers rescued four ducklings.
But immediately afterwards, the mother duck waddled across motorway with five more ducklings and headed toward the Schweizerhalle Tunnel, about 400 metres from the exit to Pratteln, police said.
The birds almost certainly would been run over by vehicles.
But police decided to close the three lanes of the motorway in the direction of Bern and Lucerne to get the ducks safely off the road.
The road was only closed for five minutes but police acknowledged this led to traffic delays as cars backed up.
The A2 motorway is a major route linking the north of Switzerland (Basel) with the southern canton of Ticino (Lugano and Chiasso) and the country's border with Italy.