The tusks, valued at nearly 10 billion naira or over $11 million, were crushed in the capital Abuja.
"They are most beautiful on the elephants and we should leave them on the elephants."
Mark Ofua, West Africa representative for the Wild Africa Fund, said the ivory had been stockpiled over years.
"And today we have brought everything out to say, we want to make a public show of destroying them to mark an era when Nigeria says no to illegal wildlife trade, no to destruction of our biodiversity, no to destruction of our wildlife."
Over the past three decades, Nigeria's elephant population has plummeted from an estimated 1,500 to less than 400.
Conservationists say that's due to poaching for ivory, habitat loss and human-elephant conflict.
Nigeria is considered a hub for gangs sending illegal African wildlife parts to Asia, according to law enforcement and experts.
But counter-smuggling efforts have been stepped up in recent years.
"...and I can assure you that any perpetrator in illegal wildlife trade in tusks, both those that go out to do the killings, those that do the buyings and those that do the trading, when caught will be fully dealt with according to the law."
Tuesday's event follows a similar one in October when officials destroyed four metric tons of seized pangolin scales valued at $1.4 million.
Nigeria's Environment Minister Iziaq Salako said the powder from the elephant tusks would be used to build a symbolic national park monument - a reminder of the importance of elephants in the ecosystem.
