In what is thought to be a legal first, Mohammed Zaman, 53, from near York in northern England, was convicted of the manslaughter of Paul Wilson, a 38-year-old customer.
Wilson had asked for a chicken tikka masala with no nuts but it was cooked with a groundnut mix containing peanuts.
He was found slumped in the bathroom at home in January 2014, after suffering a severe anaphylactic shock.
Just three weeks before Wilson died, a 17-year-old had suffered an allergic reaction at another of Zaman’s restaurants after being assured that her meal would not contain nuts. She required hospital treatment.
Prosecutors said that Zaman, who owned six restaurants in the area, had switched from more expensive almond powder to the groundnut mix to save money. He also employed untrained, illegal workers.
Judge Simon Bourne-Arton said Zaman had thrown away everything he had worked for “in pursuit of profit”.
“You have done so in such a manner as to bring about the death of another individual. Paul Wilson was in the prime of his life,” he said.
“He, like you, worked in the catering trade. He, unlike you, was a careful man.”
The Crown Prosecution Service said the sentence showed that all those in the catering industry had a “duty of care” to their customers.