A brawl at a six-year-old's birthday party in Sydney's south-west last month has led to the arrests of seven people.

The six men and one woman were charged with a range of offences, including assault and affray.

Three men were taken to hospital after the fight, which lasted about five minutes at Wetherill Park's Lollipops Playland centre on Sunday, June 21.

The play centre was busy at the time and children could be seen hiding and crying on video footage, which was later shared online and viewed thousands of times.

A woman was arrested at a home in Sydney this morning. ( Supplied: NSW Police )

"The behaviour that we saw at the play centre was something that I just cannot understand," Fairfield Superintendent Peter Lennon said.

"There are a number of children who can be seen on the footage who are extremely upset and crying."

At the time, police said they were investigating reports a fight between two groups was sparked when a man pulled a girl's hair.

It was believed a 48-year-old man, who was accused of pulling the six-year-old's hair, was injured after being confronted by men from another group.

Two other men from his group were also injured when they intervened.

"They're OK, they've been assisting police with their inquiries and I understand they've all recovered from their injuries," Superintendent Lennon said.

"The incident started over two young girls — the oldest was six years of age — having a minor dispute as maybe young girls do in playground centres.

"[It] escalated into a number of men and at least one woman engaging in what I would call a brawl, which lasted for five or six minutes, at a children's play centre.

"I can't understand people's reactions in that circumstance."

Superintendent Lennon said five homes across south-west Sydney were searched this morning.

Clothes and other items were seized and police arrested:

a man, 35, at Middleton Grange

a man, 35, at Middleton Grange a man, 61, and a woman, 31, at Hoxton Park

a man, 61, and a woman, 31, at Hoxton Park a man, 38, at Greenfield Park

They were taken to Fairfield and Green Valley police stations.

Three other people later turned themselves in to police.

Police said all those charged were from the same extended family and were on one side of the disagreement.