Binmen walked out in Sandwell on Tuesday in the first of four planned strikes.
Residents were told to put their bins out as normal but were warned of potential delays to collections as a result of the action.
Striking workers gathered outside Serco's Sandwell depot.
The industrial action comes after a long-running row between unions and Serco, which is contracted by Sandwell Council to run waste services in the borough.
Some workers voted to strike following allegations of bullying and unhappiness about working conditions.
Gill Ogilvie, West Midlands senior organiser for the GMB Union, said: "Fantastic support from the public this morning solidarity with the GMB bin workers standing up to the bullies.
"Sandwell Council needs to step up and start getting their contracts in order and stop believing the lies."
Serco said constructive talks had been held over the last few weeks but it was not able to prevent the action. Further strikes are planned on Tuesdays during September.
Sandwell Council said its focus is to ensure disruption “is kept to a minimum”.
Garden waste collections are being suspended from Monday to Friday to allow the remaining staff to concentrate on the collection of domestic waste and recycling bins.
Council bosses said if the bins in a particular street are not emptied on the usual day, they should be left out and they will be emptied as soon as possible.
The authority said on Twitter: "If the bins in your street are not emptied, please leave them out and they will be collected as soon as possible.
"Garden waste bin collections are suspended for all residents this week.
"We apologise in advance for any inconvenience caused."