As some 200 demonstrators rallied outside, the men's tennis world number one spent his third day in Melbourne's former Park Hotel, which now holds some 32 people under Australia's stringent immigration policy. Djokovic had a rude welcome at Melbourne airport Wednesday night: his lawyers say border control agents held him for eight hours before cancelling his visa and sending him to the facility.
Detainees cannot leave the building and nobody is allowed in or out except staff.
The five-storey centre gained notoriety last year when a fire forced migrants to be evacuated, and maggots were allegedly found in the food.
But the nine-time Australian Open champion's pleas to be moved to another facility so he can practice for the tournament as he appeals the visa decision have fallen on deaf ears, his lawyers say.
"Can you imagine what the mother's going through -- the son prisoner?" asked 47-year-old protester Raymond Stankovic outside the building.
"You know how he's got a strict diet and everything and the food that they give him, it's just, you wouldn't probably give your dog some of the things. There's probably cockroaches and stuff."
A migrant rights activist, though, bemoaned the lack of attention afforded to refugees compared to the intense media focus on Djokovic.
"I'm kind of disgusted, to be honest, that it's taken Djokovic being here to get any attention on the plight of the refugees," said Asher Preston, 34.
"Compared to what Djokovic is facing for a couple of days or whatever, what the refugees in here are going through for years on end is, you know, utterly atrocious," he added.
It sort of disgusts me that that the media has largely ignored it, to be honest," Preston said. "And yet politicians are getting away with absolutely abusing refugees."
The day began under drizzle with a dozen or so immigrant and refugee rights activists as well as fans of the 34-year-old Serbian.
But in the afternoon, scores of people protesting Covid-19 vaccination mandates joined in, many of them peeling off from a separate demonstration in another part of the city.
Across the road from the centre, they waved flags and brandished placards reading "No more lockdown, vax or unvax"; "Stand now or kneel forever"; and "Push back! Don't comply!"
Children and families joined in, too.
"I want to tell him: 'Hold out Novak. We are with you'," said 63-year-old Lisa Pavicevic.
"He is setting a good example. He could have got on a first-class flight back to Serbia but he is fighting for his convictions."
Fellow protesters joined in a form of Serbian line dancing.
At the anti-vaccination rally elsewhere in the city, there were signs of support for the tennis ace.
"I don't want to see my grandchildren vaccinated," said Margaret Beacham, a 67-year-old former primary school teacher.
"Novak is making a stand and it's a worldwide opportunity for him to say something about vaccination status and how ridiculous it is."
Above the main door to Djokovic's temporary Australian abode, yellow-paint graffiti read: "Free Them All".A few steps away, a protester wearing a cap, headphones and an anti-viral mask held up a placard: "Aussie Open? More like Aussie endlessly abusing refugees."