The two Sydney rivals meet at Allianz Stadium on Saturday night, where the Sky Blues are unbeaten in the past five derbies.
Hamill said on Wednesday that playing at Allianz was like a home game for Wanderers, claiming there was a 60-40 split in support in favour of Western Sydney.
O'Neill ignored those claims, labelling Allianz as their 'fortress' and pointing out Sydney's home record where they were undefeated in the A-League last season, winning 12 out of 15 home games, including finals.
"Allianz is our home. It's where we play our best football," O'Neill said.
"I think it's a fortress for us. We have our fans there every single week making sure we put in a good performance and get the win.
"We've proven that this season and the fans are a massive help for us."
Polish recruit Adrian Mierzejewski remains in doubt for the game, after picking up a hamstring complaint in Sydney's 3-2 win over Wellington on Sunday.
The attacking midfielder trained away from the main group on Wednesday but Sydney remain hopeful he'll play on Saturday.
"He's good. He's doing everything he can to make sure he's on that park on Saturday," O'Neill said.
"He came here and he knew the reputation that the Sydney Derby has. He mentioned to a few of the boys that's one game he certainly wants to be playing in.
"He'll be doing everything he can to be ready for Saturday."