Shahram Forozandeh, 44, was prosecuted by the transport department for wearing the trousers contrary to industry standards when he was stopped during a routine inspection in January, the Adelaide Advertiser reported.
In South Australia state, taxi drivers must wear smart business-style shirts and trousers, with jeans and tracksuit bottoms banned.
Forozandeh protested that his outfit was "purely wool and tailor-made".
"I had no idea that it would be considered as not wearing a uniform as the material was pure wool," he said.
Magistrates slapped him with a Aus$265 fine plus Aus$1,150 in costs.