"Customers are entitled to rely upon the accuracy of information provided to them about the products that they buy and this was especially important for a product that may be used for personal protection at work," Commissioner Anna Rawlings said.
In the sentencing, judge Mary-Beth Sharp said Argyle's offending was "highly careless if not grossly negligent."
Sharp said its claims had the potential to cause "huge" harm in the event of an electrical fire.
"Fortunately a small number of products were supplied, most have been retrieved and no harm has been done," she said.
The Commerce Commission first alerted Argyle to its concerns in May 2016. The company then removed the jackets from sale and undertook a voluntary recall.
Nine jackets were recalled and customers were refunded.
Argyle CEO Craig Broomhall told the Herald his company did not make the jackets it sold and was misled by a manufacturer.
He would not name the company or say if he intended to take legal action against it.
"This isolated issue has galvanised us as a business to do better and to support our team more and improve our processes and support our customers."
He said he commissioned independent testing on the jackets as soon as the issue was brought to his attention by the Commerce Commission.
"Certification and reports on the safety standards of products can now be made available to our customers on request."