Thirty people are protesting in the Blacktown Council building lobby now after five dogs were put down at Blacktown Pound late last week.
The protesters arrived at the council building about an hour ago.
Melanie Norman, of Pound Rounds, an animal welfare group, said that the council had been working towards being a "low kill" council.
"Their goal has always been to re-home pets and we've had a fabulous relationship with them, until now," Ms Norman said.
"Seven dogs remained on their kill list and five of them were euthanised on Friday."
She said their protest was a peaceful one.
A Blacktown Council spokeswoman confirmed that there were some people in the lobby of the council, but the council has not yet issued any further comment.
The Sun has sent the council a list of questions and will update the story with their response as soon as possible.