Fans started lining up at least a day before to get inside as floor tickets were general admission.
"It's kind of like a little community," said Carmen Trevino Almanza on Tuesday who had spent the night in a tent across from the SAP Center.
MORE: Taylor Swift's The Eras Tour at Levi's Stadium
"I knew that I wanted to camp out and be the first person to try to get in here," she said. "So I tried to come as early as I could."
Her tickets were for night two of the Eilish concerts in San Jose so, she had another night to go.
Others, across the street, got in line early Tuesday to try to get last-minute tickets directly from the box office.
"We weren't able to get tickets during pre-sale so we just thought we could get cheaper tickets here," Ceasar Aranda from Tracy.
Emily Phan is from San Jose and currently attending college in Santa Cruz.
MORE: Music legends The Rolling Stones rock the stage at Levi's Stadium
"We got situated at 4:30 a.m.," she said. "It's been a long, night, morning, whatever you want to call it. I'm studying for finals right now, too."
The "Hit Me Hard and Soft" Tour has been one of the Bay Area's most anticipated music events of the year.
Caltrain even devoted a special car to take fans to and from the venue on night one of the San Jose shows.
"We're going to have a themed Billy Eilish car. We're going to be on board, giving away both Caltrain and Billie Eilish Merch," said Dan Lieberman, Caltrain Public Information Officer.
Local restaurants and food vendors inside the SAP Center got a special request.
MORE: Just how much is Taylor Swift's tour helping businesses? Find out here
"They said, 'Hey, can you do all vegan?' and we said, 'Let's make it happen,'" said Randy Musterer, Owner of Sushi Confidential.
A request he said the business worked nonstop to accommodate.
"We're excited. It's a sold-out show tonight and tomorrow night, so, we're ready for the challenge," Musterer said.
Still, no one is more excited than those diehard fans.
"Her music and just like her overall message," said Trevino Almanza. "It really does touch me."