When the plane landed, he was met by five police officers, who let him go without further incident.
"Qantas, your racist flight attendant was beyond rude and took it to the next level by calling the police on me. Thank god the other passengers testified that she was out of control. The police finally let me go. Imagine if the police were as aggressive," he said.
"Is calling the police on a passenger for not hearing the PA due to wearing noise cancelling headphones appropriate?
"I did comply quickly and politely, only to be greeted by police. I think I was targeted."
He went on to allege the flight attendant "singled every person of colour in the flight and gave them a hard time", and that "other passengers on the flight agreed that she was out of hand".
The singer also retweeted a couple of people who said they were on the same flight, and agreed with him.
Meanwhile, he hit back at suggestions he was intimidating the flight attendant in question by singling her out and naming her online. News.com.au has not named her for legal reasons.
"I am posting so that this doesn't happen again. It shouldn't happen to an Aboriginal, Latino, African, LGBTQ white, red or anyone. Everyone deserves to be treated with respect," he said.
He said he did not "wish any harm to anyone" and merely wanted everyone to be "respected and treated with dignity".
Qantas has denied the incident was race-related, instead putting it down to a "misunderstanding".
"There was a misunderstanding on board, which seems to have been exacerbated by will.i.am wearing noise cancelling headphones and not being able to hear instructions from crew," a spokesman for the airline said.
"We completely reject the suggestion this had anything to do with race. We'll be following up with will.i.am and wish him well for the rest of the tour."
The Black Eyed Peas are headlining an event at Homebush in Sydney's west this evening.
Qantas was involved in another celebrity spat in September when The Veronicas were kicked off a flight travelling in the opposite direction, from Sydney to Brisbane.
Twin sisters Lisa and Jess Origliasso were removed from the flight after they "refused to follow crew instructions" and were deemed security risks.
They claimed the incident was "escalated without explanation" from cabin staff, and was "incredibly intimidating and confusing".
It resulted in the plane being stuck on the tarmac for 45 minutes.
There were conflicting accounts from passengers at the time, with some backing the sisters' assertions that Qantas had been unreasonable, and others accusing the pair of being "belligerent".
Qantas said they had "refused to follow crew instructions and were offloaded".