Tim Smith, 51, bought the £1.50 Centennial pistachio nuts from the Tesco superstore on Vimy Road, Linslade on June 12.
But when daughter Claire, 21, bit into one of the nuts, she was horrified to find the dead maggot inside.
Tim, of Wantage Close, said: “Just literally by chance she was eating them and glanced down and in one of them she saw the maggot.
“I was annoyed and I know things can happen, but their reaction was ‘oh dear’.”
Tim added: “To say that she felt sick or was put off eating pistachios for life is an understatement.
“It was disgusting, and we don’t know how many of those she’d eaten.”
After getting in touch with Tesco customer services department, Tim took the Tesco discount brand product back into the store on Thursday.
He said: “They took the product but they weren’t very apologetic.
“I asked to speak to a manager and I was told ‘no’ by the person on the customer service desk.
“When I asked if I would be hearing back, they said it would probably be a case of if and when.”
Tim was refunded the £1.50 cost of the pistachios and sent on his way.
A Tesco spokesman defended the company’s record on food and hygiene.
He said: ‘We set ourselves the highest standards for the products we sell and are always disappointed when a customer has reason to complain.
“We have let Mr Smith know the product will be sent to the product’s manufacturer for investigation and we will update him as soon as we can.”