Scores of customers were ushered out of the newly opened store at 2.45pm as alarms sounded following an announcement over the tannoy system that there had been a 'technical difficulty'.
Less than two hours later reports emerged on social media that hundreds of people had again been evacuated from the store for a second time.
Ikea has not yet commented publicly on why the evacuations took place - but shoppers caught up in the drama described chaotic scenes.
Mitchell Lilley, aged 21, of Wickersley, was visiting with his 19-year-old girlfriend Danielle Buck when the first evacuation took place.
He told how people were told to abandon items they had purchased and had to leave meals they were halfway through eating.
He added: "We were at the food court when they announced it over the speakers.
"Then an alarm went off and we were all ushered towards the fire exits.
"We had to go down some stairs which were only about 4ft wide and ended up in the car park.
"Then another alarm sounded and we were told to leave our cars and go to the fire assembly point.
"We were there about 15 minutes and then the alarms stopped and everyone started to leave."
Mitchell described the fire exits as 'overcrowded' and told how members of staff seemed unaware why the alarms had gone off.
He added: "It was very crammed on the stairs. I know it has only just opened but members of staff didn't seem to know what to do.
"I don't know if it was a false alarm or what, but it didn't give me great confidence if there had been a real fire."
Details emerged on Twitter at about 4.30pm that customers had been asked to leave for a second time. A picture appeared to show police at the scene.
One customer who was at the store said: "Ikea isn't getting off to the best of starts."
Another described it as a "totally shambolic opening weekend."
We rang Ikea but a woman said she was not allowed to give details to the media.
The company which handles media enquiries for Ikea have been contacted and we are awaiting a reply.
South Yorkshire Police and South Yorkshire Fire and Rescue have also been contacted.