The planned protest was welcomed by the factory workers' union, E tū.
"To date the community has not had a forum to express its support for Cadbury and this will be the perfect opportunity," said union spokesman Neville Donaldson.
"If people care about Cadbury, they should seize this chance to make their voices heard, and express their anger and frustration at Mondelez for this misguided proposal."
The union had been in talks with Mondelez about their proposal, however, the company had shown "little interest in working through the issues or any concerns about the effect on staff", Donaldson said.
"A strong show of opposition on Saturday to its plans for Cadbury may persuade them it's time to take the consultation process seriously and reconsider."
- Additional reporting NZ Herald