Fonterra has been fined nearly $175,000 for discharging wastewater from its Edgecumbe plant into Bay of Plenty waterways.
The Bay of Plenty Regional Council prosecuted Fonterra over four failures of its whey irrigation system and two overflows of wastewater in September 2014 and April 2015.
Fonterra pleaded guilty to six separate offences under the Resource Management Act.
The council said it hoped the conviction would prompt the company to set higher standards for environmental protection.
It said wastewater could kill fish in rivers and streams.