A policeman and two civilians were arrested as they tried to sell 25kg of ivory worth more than Sh1 million.
Kenya Wildlife Service spokesman Ngugi Gachaga said the men had identified "a buyer" for five elephant tusks and approached him to sell the ivory to him.
"Through our intelligence, we were able to arrest them as they tried to sell off the ivory. They are under interrogation and will take plea soon," he said.
Gachaga said they are yet to establish the source of the ivory and that the seizure reveals up to three elephants were slaughtered.
He said the arrest indicates some state agents were involved in the crimes but vowed their crackdown will continue.
The three were locked up at the Langata Police Station ahead of their arraignment today where they face possession and trafficking of ivory charges.
This is the latest such arrest in the city. Last year, three other officers were arrested after they were found with similar ivory.
Poaching in the region is on the rise.