Martin McGowan took legal action against Scottish house builder Springfield Properties.
The Court of Session heard that McGowan worked as a subcontractor for Springfield employing up to 70 people on their projects.
Both sides fell out in 2016 when McGowan raised concerns about asbestos and a lack of PPE for his staff on a number of sites.
Springfield responded by obtaining an interim court order to prevent McGowan speaking publicly about the asbestos.
The order was eventually lifted in 2021 after Springfield was fined £10,000 for Health and Safety offences involving asbestos at a site in East Dunbartonshire.
McGowan said the gagging order hit his reputation and led to him losing contracts.
The Court of Session ruled in his favour and awarded McGowan £558,033.
A Springfield Properties spokesperson said: “We strongly disagree with this judgment, and we fully intend to appeal it.
“This decision is not related to the previous asbestos case – raised in 2014 and fully investigated by the HSE and SEPA. It did not investigate nor confirm any of Mr McGowan’s claims, all of which had previously been interrogated and rejected by the relevant authorities.
“The interdict was sought solely to prevent the persistent spread of claims by Mr McGowan and this decision does not relate to, nor reopen, the historic investigation.”