The retail giant was charged under the Occupational Health and Safety Act after a 17-year-old employee at a store in Grand Falls was electrocuted on Jan. 5, 2011.
Patrick Desjardins was using a floor buffer on a wet floor in a garage at the time.
Crown attorney Karen Lee Lamrock says Denis Morin, who was a supervisor at the store, also pleaded guilty to two charges under the act.
She says Walmart was fined $120,000 and Morin $1,056.
WorkSafeNB, the Crown agency responsible for the act, has said Desjardins was using an inappropriate floor polisher and a faulty extension cord when he died.
The company says in a statement released Tuesday that it co-operated fully with the investigation and has brought in changes to prevent similar accidents from happening.
WorkSafeNB has said the polisher Desjardins was using hadn't been inspected and was in poor working condition.
The agency issued several orders against Walmart after the death and it says the company has complied with those orders.
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