In March the Grill restaurant owned by Andersson in central Stockholm was attacked with a Molotov cocktail. Last month four people, including the father and son, were formally charged on a range of offences including attempted extortion, attempted arson, and weapon crimes.
Swedish media reported that the 37-year-old was linked to an organized criminal network. In the Stockholm district court he was identified as the ringleader of the whole operation.
According to the prosecutor the threats began when Andersson wanted to stop using the 37-year-old's company, which he had hired to do the washing up and general cleaning for his restaurants.
What followed was an attempt to extort money from Andersson and then the attempted arson in March.
The attack ultimately proved unsuccessful, as Grill was equipped with reinforced windows which repelled the flaming bottle back onto the street.
The chef's lawyer, Claes Borgström, said that his client was pleased with the verdict for the most part, but was unhappy with the 25,000 awarded in damages. Borgström had demanded double that sum.
"I think it is too low. It was a very serious offence for Melker Andersson. But his interest was not really the money, just that they were convicted," the lawyer told the TT news agency.
Meanwhile the lawyer for the 37-year-old said he will be appealing to the verdict. He also said it wasn't an extortion attempt, claiming that a debt existed between Andersson and his client.
The man is set to spend the next four years behind bars, while his 17-year-old son will spend eight months in a juvenile correction facility.
The two others involved in the attack were sentenced to fourteen months and eighteen months in prison respectively for their role in the arson.
Grill is one of eight restaurants which the celebrity chef runs in the Swedish capital. In 2007 another of his restaurants was burned to the ground in an apparent arson attack.