A diner at a Sydney restaurant has posted a video of a "horrible experience" where she was served a steak covered in live maggots.

Stella Kim said she was dining at The Ranch in North Ryde to celebrate a 1,000-day anniversary with her boyfriend last Wednesday, and was served a steak "full of worms".

Ms Kim posted a video to her Facebook page which appears to show a steak crawling with maggots.

"Live worms [were] coming out of the steak," she said in her post.

"We couldn't believe this was happening at one of the big restaurants in Australia ... don't know how many people are affected by this.

"I wish no-one has to go through this horrible experience. We have lost our appetite."

Stella Kim said she was dining at The Ranch in North Ryde. ( ABC News: Andrew Whitington )

The video has been shared and commented on thousands of times.

Ms Kim said the restaurant offered them a refund and $150 in vouchers.

Andrew Yong, legal officer for the ALH Group which owns The Ranch, told the ABC the restaurant had apologised to Ms Kim but he was not sure if compensation had been offered.

He said The Ranch had conducted its own internal investigation into the incident and had determined the maggots were likely laid after the steak was cooked.

Mr Yong said it was an isolated event at The Ranch and more than 260 steaks were served that same night without incident.

He said the company had spoken to City of Ryde Council and were happy for them to conduct any investigations into the incident.

Stella Kim said she reported the incident to the NSW Food Authority and North Ryde council. However, the NSW Food Authority said it had not received a complaint.