In a statement to Sun Online Travel, Ryanair confirmed the staff members had been dismissed.
"All six cabin crew members in Porto were dismissed on Monday, November 5 for breach of contract on grounds of gross misconduct, after staging a fake photograph to support a false claim (widely reported in international media outlets) that they were 'forced to sleep on the floor' of the Malaga crew room," the low-cost Irish airline said.
"(This) was behaviour which damaged their employer's reputation and caused an irreparable breach of trust with these six persons."
When the photo was released last month, union representatives claimed the 24 crew members had been forced to spend more than seven hours in the office with only seven chairs, before being taken to a VIP area to sleep on sofas.
Ryanair then released CCTV footage showing the crew lying down on the floor to pose for the photo.
However, the video backfired and members of the public attacked the airline on social media.
One commenter wrote on Twitter: "Everyone already KNEW it was a protest picture you knuckleheads! The fact remains: you stranded FOUR CREWS in an airport terminal for the night and made no discernible attempt to find them proper lodging or even food and water!"
The airline admitted the crew had spent "a short time" in the room due to a shortage of hotel rooms on the night, but denied anyone had slept on the floor.
But union delegate Fernando Rikote said the crews flew back to Porto the next morning "without proper rest, without sleeping at all" – and were denied food on the aircraft.