The person, who cannot yet be identified for legal reasons, pleaded guilty in the Christchurch District Court to possession and supply of the illegal party drug MDMA (ecstasy).
It comes as several other Canterbury-based harness racing people continue to face district court proceedings over possessing and supplying ecstasy, a class B drug.
They were caught up in the ongoing police undercover and electronic surveillance operation, Inca, which is looking into drug use and alleged race fixing in the harness racing industry.
One trainer/driver, Matt Anderson, pleaded guilty to possession and supply.
Anderson will now face a hearing over the drug matter from racing industry statutory body, the Judicial Control Authority. He could lose his training and driving licence and face a substantial fine.
The latest individual to plead guilty has a district court hearing in early April, where their lawyer will argue for a discharge without conviction and permanent name suppression.
Harness Racing New Zealand chief executive Peter Jensen said recreational drug use is an issue that it takes seriously.
"Our sport is not immune to what is a societal issue present in all professions and trades.
"As a condition of their licence, licensed participants such as trainers, drivers and stable hands can be, and are, tested at race or trials meeting by the Racing Integrity Unit,” he said.
“A number of drivers were tested at a race meeting last week and all tests were clear.”
New Zealand Harness Racing Trainers and Drivers Association secretary Peter Cook did not think recreational drug use was widespread.
“The fact that one or two individuals have been doing it does not mean to say that recreational drugs are rife in the industry,” he said.
“I’m not saying it is not there, I just don’t think it is a big problem,” he said.
“I know some of the drivers that do long hours, they tend to do eight hours a day at the stable and then drive to Dunedin and then home again, some pretty long days and some say they need some stuff to keep them going.”
Health agencies and the police are concerned about the use of ecstasy in society, particularly in the party scene.
Ecstasy gives a person an enhanced sense of well-being, increased extroversion, and they become highly affectionate.
But use of even moderate doses can dramatically increase body temperature, with potentially deadly consequences.
Meanwhile, a Canterbury harness trainer/driver has been arrested on strangulation and assault charges. He is due to appear in the Christchurch District Court later this month.
