Mr Hashman, 43, had been seeking £50,000 for loss of earnings and injury to feelings from bosses at Orchard Park Farm garden centre near Gillingham, Dorset.
They sacked him in September 2009 two days after his covert filming had helped to convict the celebrity chef Clarissa Dickson Wright of illegal hare coursing.
He today agreed an undisclosed settlement, believed to be a five figure payout, after a panel at Southampton Employment Tribunal ruled in his favour.
Married father-of-two Hashman, of Shaftesbury, Dorset, successfully argued that his views on fox hunting should be placed on the same legal footing as religious beliefs.
It was accepted that his concern about the environment, animal rights, veganism and, in particular, his opposition to fox hunting, amount to a philosophical belief under the Employment Equality (Religion and Belief) Regulations 2003.
Hashman’s solicitor Shah Qureshi, of law firm Bindmans, said: "This is clearly a very positive tribunal decision for those who believe in animal rights.
"It means that employers must, in future, be aware that they cannot discriminate against people who have strong views or beliefs about the rights of animals, in particular regarding fox hunting.
"And it shows that the courts will take a considered approach case by case to protecting the beliefs of a person when they have been discriminated against on the basis of their beliefs."
Giving evidence, professional gardener Mr Hashman told the tribunal how he lost his job when his bosses found out he was a leading saboteur and animal welfare activist.
When he took the job of creating a demonstration garden, he was "blissfully unaware" that its owners were keen supporters of the South and West Wiltshire Hunt
Likewise, owners Sheila and Ron Clarke had no idea that he had been an influential hunt saboteur since the age of 14, the tribunal heard.
Hashman said he was "picked on" and suddenly sacked after he appeared on Radio 2's Jeremy Vine Show, explaining his part in Dickson's Wright's court case.
He told the tribunal: "I believe now that my involvement in relation to hunting issues and ultimately my philosophical belief was the reason for my dismissal.
"On September 1, 2009 there were two convictions at Scarborough magistrates' court under the Hunting Act, which I was directly responsible for.
"One of those convicted was celebrity chef Clarissa Dickson Wright. I wrote a personal blog about this and also on that day appeared on the Jeremy Vine Show.
"I believe that those connected with Orchard Park knew, or came to know, of some or all of these matters at some point leading up to my dismissal."
Orchard Park Farm had claimed that it only dismissed Hashman because his vegetable patch at the garden centre, designed to encourage customers to grow more produce, was not making enough money.
Speaking ahead of the judgment, Hashman said: "It is my fundamental belief that it is wrong to kill animals for sport.
"I don’t think anyone should be discriminated against at work because of their views on issues such as hunting.
"Hunting arouses huge passions for and against but in the workplace, work should be work.
"It is unacceptable that I should suffer in the workplace because I feel strongly that hunting is morally wrong.
"Politics and morality as to how we live our lives should not be brought into the workplace.
"This is how people behaved years ago. I thought we had grown up as a society so that people with fundamentally opposed views on issues could live and work alongside each other.
"We have all got to breathe the same air, drink the same water and share the same space after all."