Jason Lawrence explained how he, his wife Denise, 37 and their eight-year-old daughter had almost eaten the entire bag of Clancy's Roasted and Salted pistachios from Aldi when he picked out one that 'looked a bit too dark'.
He opened up the shell, and to his horror he found a dead maggot inside.
"I shouted my wife to come and take a look at it, and my little girl came too, and after she saw the maggot she was sick twice.
"She had been eating them too, but I think it came on a bit too quickly for it to be because of that," said Jason, of Birley Moor Avenue, Birley.
"We had eaten the whole lot, and I kept thinking afterwards, they did seem particularly crunchy. The worst bit was the rest of that evening, waiting to see if we would be sick like Amber. But we weren't, thankfully.
The 47-year-old says he and his family shop at the Aldi store in Stanley Store, Killamarsh every week and has never had any problems before. The bag of pistachios were bought during a family shop on November 8, and were eaten three days later on November 11.
He adds that he can 'almost understand how something like this can happen' - but the thing he says he is really disgusted by is the response he received from Aldi's customer services department.
"They just didn't seem that bothered by it," continued Jason.
"They offered a Â£10 refund at first, and then after I explained that my daughter had been sick because of seeing that they came back and said they'd give me a Â£15 refund, but to me that's not really good enough.
"To me a proper good-will gesture would have been a week's shopping or something like that."
An Aldi spokesperson said: “We were sorry to hear of Mr Lawrence’s experience and apologised to him as soon as he brought this to our attention. We have advised him to bring the product back to his nearest store for a full refund.”